TUCSON, Ariz. » Moments after the swirl of panic, blood, death and shock, the suspect was face down on the pavement and squirming under the hold of two civilians, his shaved head obscured by a beanie and the hood of his dark sweatshirt.

Deputy Sheriff Thomas Audetat, a chiseled former Marine with three tours in Iraq to his credit, dug his knee into the gangly young man’s back and cuffed him. With the aid of another deputy, he relieved the heroic civilians of their charge and began searching for weapons other than the Glock semiautomatic pistol, secured nearby under a civilian’s foot, that had just fired 31 rounds.

In the left front pocket, two 15-round magazines. In the right front pocket, a black, four-inch folding knife. "Are there any other weapons on you?" Deputy Audetat recalled demanding.

"Back right pocket."

But the back right pocket contained no weapons. Instead, in a Ziploc bag, the deputy found about $20 in cash, some change, a credit card and, peeking through the plastic as if proffering a calling card, an Arizona driver’s license for one Jared Lee Loughner, 22.

Audetat lifted the passive, even relaxed suspect to his feet and led him to the patrol car, where the man twisted himself awkwardly across the back seat, face planted on the floor board. Then he invoked an oddly timed constitutional right. "I plead the Fifth," Loughner said, though the deputy had no intention of questioning him. "I plead the Fifth."

At a Pima County Sheriff’s Department substation, Deputy Audetat guided Loughner to a tiny interview room with a two-way mirror, directed him to a plastic blue chair and offered him a glass of water. The deputy detected no remorse; nothing.

Now to another building for the mug shot. Look into the camera, the suspect was told. He smiled.

Click.

Loughner’s spellbinding mug shot — that bald head, that bright-eyed gaze, that smile — yields no answer to why, why, why, why, the aching question cried out in a subdued Tucson synagogue last week. Does the absence of hair suggest a girding for battle? Does the grin convey a sense of accomplishment, or complete disengagement from the consequence of his actions?

And is his slightly blackened left eye all but winking at the wholesale violence that preceded the camera’s click? The attack on a meet-and-greet event with a congresswoman outside a supermarket; the killing of six people, including the chief federal judge in Arizona and a 9-year-old girl; the wounding of 13, including Rep. Gabrielle Giffords, shot in the head.

Since last Saturday’s shooting frenzy in Tucson, investigators and the news media have spent the week frantically trying to assemble the Jared Loughner jigsaw puzzle in hopes that the pieces will fit, a clear picture will emerge and the answer to why will be found, providing the faint reassurance of a dark mystery solved.

Instead, the pattern of facts so far presents only a lack of one, a curlicue of contradictory moments open to broad interpretation. Here he is, a talented saxophonist with a prestigious high school jazz band, and there he is, a high school dropout. Here he is, a clean-cut employee for an Eddie Bauer store, and there he is, so unsettling a presence that tellers at a local bank would feel for the alarm button when he walked in.

Those who see premeditation in the acts Loughner is accused of committing can cite, for example, his pleading of the Fifth Amendment or the envelope the authorities found in his safe that bore the handwritten words "Giffords," "My assassination" and "I planned ahead" — or how he bided his time in the supermarket, even using the men’s room. Those who suspect he is insane, and therefore a step removed from being responsible for his actions, can point to any of his online postings, including:

"If 987,123,478,961,876,341,234,671,234,098,601,978,618 is the year in B.C.E then the previous year of 987,123,478,961,876,341,234,671,234,098,601,978,618 B.C.E is 987,123,478,961,876,341,234,671,234,098,601,978,619 B.C.E."

What the cacophony of facts do suggest is that Loughner is struggling with a profound mental illness (most likely paranoid schizophrenia, many psychiatrists say); that his recent years have been marked by stinging rejection — from his country’s military, his community college, his girlfriends and, perhaps, his father; that he, in turn, rejected American society, including its government, its currency, its language, even its math. Loughner once declared to his professor that the number 6 could be called 18.

As he alienated himself from his small clutch of friends, grew contemptuous of women in positions of power and became increasingly oblivious to basic social mores, Loughner seemed to develop a dreamy alternate world, where the sky was sometimes orange, the grass sometimes blue and the Internet’s informational chaos provided refuge.

He became an echo chamber for stray ideas, amplifying, for example, certain grandiose tenets of extremist right-wing groups — including the need for a new money system and the government’s mind-manipulation of the masses through language.

In the last three months, Loughner had a 9-millimeter bullet tattooed on his right shoulder blade and turned increasingly to the Internet to post indecipherable tutorials about the new currency, bemoan the prevalence of illiteracy and settle scores with the Army and Pima Community College, both of which had shunned him. He also may have felt rejected by the American government in general, and by Giffords in particular, with whom he had a brief — and, to him, unsatisfactory — encounter in 2007.

Nearly four years later, investigators say, Loughner methodically planned another encounter with her. Eight days ago, on a sunny Saturday morning, he took a $14 taxi ride to a meet-your-representative gathering outside a Safeway, they say, and he was armed for slaughter.

EARLY SIGNS OF ALIENATION

One spring morning in 2006, a student showed up at Mountain View High School so intoxicated that he had to be taken to Northwest Hospital, 5 miles away. A sheriff’s deputy went to the hospital’s emergency room to question the inebriated 17-year-old student, whose eyes were red from crying.

According to a police report, the teenager explained that he had taken a bottle of vodka from his father’s liquor cabinet around 1:30 that morning and, for the next several hours, drank much of its contents. Why? Because I was upset that my father had yelled at me, said the student, Jared Loughner.

In the search for clues to explain the awfulness to come, this moment stands out as the first public breach in the facade of domestic calm in the modest Loughner home on Soledad Avenue in the modest subdivision of Orangewood Estates, its front door shrouded by the wide canopy of an old mesquite tree, its perimeter walled off as if for fortification.

The mother, Amy Loughner, worked as the manager of one of the area’s parks. Pleasant though reserved, she impressed the parents of her son’s friends as a doting mother who shepherded her only child to his saxophone lessons and concerts, and encouraged his dream of one day attending the Juilliard School, the prestigious arts conservatory in New York.

Once, when he was in the ninth grade, Loughner’s parents had to leave town for a week, and he stayed with the family of his friend, Alex Montanaro. Before leaving, Loughner presented Alex’s mother, Michelle Montanaro, with a document that temporarily granted her power of attorney for Jared — in case something happened.

"This is how I knew his mom doted on Jared," Montanaro said. "She thought of everything for her son."

But the father, Randy Loughner, was so rarely mentioned by his son that some of Jared’s friends assumed that his parents were divorced. Loughner installed carpets and pool decks, and spent much of his free time restoring old cars. Jared drove a Chevy Nova; his mother, an El Camino.

Some neighbors saw Randy Loughner as private; others as standoffish, even a bit scary. As a member of one neighboring family suggested: if your child’s ball came to rest in the Loughners’ yard, you left it there.

And, occasionally, word would trickle back to the homes of Jared’s friends of a family unhappy in its own way. That Jared and his father did not get along. That a palpable sense of estrangement hovered in the Loughner home.

"He would tell me that he didn’t want to go home because he didn’t like being home," recalled Ashley Figueroa, 21, who dated him for several months in high school.

Teased for a while as a Harry Potter look-alike, then adopting a more disheveled look, Jared seemed to find escape for a while in music, developing a taste for the singular sounds of John Coltrane and Charlie Parker. A talented saxophonist, he could show off his own musical chops by sweetly performing such jazz classics as "Summertime."

He belonged to the Arizona Jazz Academy, where the director, Doug Tidaback, found him to be withdrawn, though clearly dedicated. He played for two different ensembles, an 18-piece band and a smaller combo, which meant four hours of rehearsal on weekends and many discussions between the director and the mother about her son’s musical prospects.

But Tidaback did not recall ever seeing Jared’s father at any of the rehearsals or performances. And one other thing: the music director suspected that the teenager might be using marijuana.

"Being around people who smoke pot, they tend to be a little paranoid," Tidaback said. "I got that sense from him. That might have been part of his being withdrawn."

Tidaback, it seems, was onto something. Several of Jared’s friends said he used marijuana, mushrooms and, especially, the hallucinogenic herb called Salvia divinorum. When smoked or chewed, the plant can cause brief but intense highs.

None of this necessarily distinguished him from his high school buddies. Several of them dabbled in drugs, played computer games like "World of Warcraft" and "Diablo" and went through Goth and alternative phases. Loughner and a friend, Zane Gutierrez, would also shoot guns for practice in the desert; Loughner, Gutierrez recalled, became quite proficient at picking off can targets with a gun.

But Loughner, a curious teenager who at times could be intellectually intimidating, stood out because of his passionate opinions about government — and his obsession with dreams.

He became intrigued by antigovernment conspiracy theories, including that the Sept. 11 attacks were perpetrated by the government and that the country’s central banking system was enslaving its citizens. His anger would well up at the sight of President George W. Bush, or in discussing what he considered to be the nefarious designs of government.

"I think he feels the people should be able to govern themselves," said Figueroa, his former girlfriend. "We didn’t need a higher authority."

Not long after showing up intoxicated at school, Loughner dropped out. He also dropped out of band. Then, in September 2007, he and a friend were caught with drug paraphernalia in a white van.

Something was happening to Jared Loughner. It was clear to his friends, clear to anyone who encountered him.

"He would get so upset about bigger issues, like why do positive and negative magnets have to attract each other," recalled Gutierrez, the friend who joined him in target practice in the desert. "He had the most incredible thoughts, but he could not handle them."

FACING REJECTION

After dropping out of high school, Jared Loughner had tried to straighten up, friends say. He shed his unkempt image, cut drugs from his life and indulged only in the occasional 24-ounce can of Miller High Life. He began wearing crisp clothes and got a job at Eddie Bauer.

"He was damned strait-laced and, I believe, had given up weed," Gutierrez recalled. "At Eddie Bauer, he tucked his shirt in, wore a belt and dressed himself nicely, real clean cut. He could have been in any office building and would have looked fine."

And when the two friends got together, Loughner would limit himself to that one big can of beer — he was notoriously frugal — and talk of bettering himself. "He started saying that he wanted to stay out of trouble and was thinking about doing good stuff with his life," Gutierrez said.

Still, things never quite clicked.

Loughner seemed to meet rejection at every turn. He tried to enlist in the Army in 2008 but failed its drug test. He held a series of jobs, often briefly: Peter Piper Pizza, but not long enough to make it past the three-month probationary period, an executive said; the Mandarin Grill, where the owner recalled that after less than a month of employment, the teenager simply stopped showing up.

After leaving his job at Eddie Bauer, he became a volunteer at an animal-care center in Tucson. On his application, he came across as a normal and ambitious teenager, expressing interest in "community service, fun, reference and experience." But within two months he was told not to come back until he could follow rules.

At least there was the Northwest Campus of Pima Community College, where tuition was affordable, the quail often skittered across the grounds and Loughner found intellectual sanctuary. Beginning in the summer of 2005, when he was just 16, he began taking classes: music fundamentals, philosophy, sign language, algebra, biology, computers, logic — even Pilates.

But beginning in 2010, Loughner’s mostly private struggle with basic societal norms tipped into the public settings of the classroom, the library, the campus.

Pima Community College has six campuses, four educational centers and nearly 70,000 students. But one student in particular, it seems, came to occupy the attention of its administrators and security officers.

Loughner was informed in his father’s garage that he was suspended. Not long after, the college sent him a letter saying that he would not be welcomed back until he presented certification from a mental health professional that he was not a threat. That never happened.

By now the strange presence that was Jared Loughner was known in places beyond the Northwest Campus of Pima Community College.

LEAVING AN IMPRESSION

At a small local branch of a major bank, for example, the tellers would have their fingers on the alarm button whenever they saw him approaching.

It was not just his appearance — the pale shaved head and eyebrows — that unnerved them. It was also the aggressive, often sexist things that he said, including asserting that women should not be allowed to hold positions of power or authority.

One official with knowledge of the situation said Loughner once got into a dispute with a female branch employee after she told him that a request of his would violate bank policy. He brusquely challenged the woman, telling her that she should not have any power.

"He was considered to be short-tempered and made people at the bank very uncomfortable," said the official, who spoke on the condition of anonymity because the person was not authorized to discuss the matter.

The bank’s employees could not forget how, after bullet-resistant glass was installed at the bank, Loughner would try to stick his finger through a small space atop the glass and laugh to himself.

A BUSY MORNING

At 9:41 last Saturday morning, a 60-year-old cabdriver named John Marino pulled his Ford Crown Victoria into the parking lot of a Circle K convenience store on West Cortaro Farms Road to collect his first fare of the day. The cashier inside raised her finger to signal one minute.

Then out came his customer, just another customer, a normal-looking young man. Climbing into the back seat, the man said he needed to go to the Safeway supermarket on Oracle Road, on the Northwest side. Their 5-mile ride began.

Marino has been driving a taxi for a dozen years; he likes to say that he has hauled everyone from the worst crack whore to the mayor of the city. He does not pry for information from his passengers, mostly because he doesn’t care. But if a customer wants to talk, he will talk. He glanced at his rear-view mirror and saw his passenger looking out the window. The passenger was quiet, until he wasn’t.

"Do you always remember everybody you pick up?" Marino recalled the man asking.

"Yeah, vaguely," Marino says he answered. "I’ve been doing this a long time. It’s hard to remember everybody."

At another point, the passenger blurted out, "I drink too much." To which the cabdriver answered, "Oh, that’s too bad."

Then it was back to silence.

Now the cab was delivering its passenger in a hooded sweatshirt to his destination, the Safeway supermarket plaza, where a congresswoman was about to greet constituents. Loughner pulled out the Ziploc bag where he kept his cash and handed Marino a $20 bill for the $14.25 fare. The driver could not break the bill, so the two men went into the supermarket to get change.

Marino got in line at the customer-service desk, behind someone cashing in a winning lottery ticket. He received a few bills for the $20 and handed Loughner a $5 bill — meaning his tip was 75 cents. The cabdriver would later wonder why, considering what was about to happen, his passenger didn’t just let him keep the $20.

Before going their separate ways, Marino recalled, Loughner asked, "Can I shake your hand?"

Sure.

"And I noticed his hands were really sweaty," recalled the cabdriver who had seen all types. "You know?"