BIRMINGHAM, England >> Long before his short stints in jail turned into years behind bars, Khalid Masood was known as Adrian Elms, with a reputation for drinking and an unpredictable temper.

At least twice he was convicted of violent crimes, well before he stabbed a police officer to death Wednesday in London with a motion that one horrified witness described as “playing a drum on your back with two knives.”

But as he checked out of his hotel to head toward London for his deadly rampage, the manager said he was struck by his guest’s friendly manner.

Within hours, Masood drove his rented SUV across the crowded Westminster Bridge, leaving a trail of dead and wounded. Then he jumped out and attacked Constable Keith Palmer, an officer guarding Parliament, stabbing him to death before being shot to death by police.

In all, he killed four people and left more than two dozen hospitalized.

Masood, who at 52 is considerably older than most extremists who carry out bloodshed in the West, had an arrest record dating to 1983. The violence came later, first in 2000 when he slashed a man across the face in a pub parking lot in a racially charged argument after drinking four pints, according to a newspaper account.

The victim, Piers Mott, was scarred for life, said his widow, Heather.

Masood’s last conviction was in 2003, also involving a knife attack. It’s not clear when he took the name Masood, suggesting a conversion to Islam.

Heather Mott said Masood appeared to come out of jail “even worse.” She said she got chills when she learned the identity of the London attacker.

“What a pity they didn’t realize he was a nutter,” she said.

Police are combing through “massive amounts of computer data” and have contacted 3,500 witnesses as they look for clues as to why the British-born man launched the deadly attack.

“Clearly that’s a main line of our investigation is what led him to be radicalized: Was it through influences in our community, influences from overseas or through online propaganda? Our investigations and our arrests will help in that, but the public appeal will make a big difference if people come forward with more information,” said Britain’s top counterterrorism officer, Mark Rowley.

A security official who spoke Friday on condition of anonymity because he was not authorized to speak about an ongoing investigation confirmed that Masood had spent time in Saudi Arabia but said investigators were still trying to determine how long he stayed and what he was doing.

Prime Minister Theresa May said Masood was “investigated in relation to concerns about violent extremism” years ago. But she called him “a peripheral figure.”

The Islamic State group described Masood as “a soldier,” claiming responsibility for the attack. Rowley said police are investigating whether he “acted totally alone inspired by terrorist propaganda, or if others have encouraged, supported or directed him.”

People made arrests across the country as they investigate whether anyone else helped Masood prepare his attack. Six people were released without charge Friday night, leaving four in custody on suspicion of preparing terrorist acts.

Detectives have searched 21 properties in London, Brighton, Wales, Manchester and the central English city of Birmingham in one of Britain’s biggest counterterrorism operations in years. Wednesday’s attack was the deadliest in Britain since suicide bombers killed 52 commuters on London’s transit system on July 7, 2005.

Once Masood’s identity became known, police and the media began tracing his final hours.

The manager of the Preston Park Hotel in the beachside city of Brighton where Masood stayed the night before the attack said he seemed unusually outgoing and mentioned details about his family, including having a sick father.

“He was normal, in fact friendly, because we spent possibly five or 10 minutes talking to him about his background and where he came from,” Sabeur Toumi told Sky News. He was “laughing and joking, telling us stories about where he lived.”

Police raided the room, searching for clues about Masood.

Masood’s mother lives in rural Wales, according to a website on which she sells handmade cushions and handbags. The listings on Folksy by Janet Ajao have been taken down, but in an archived version of the site, she describes living in “rural west Wales with my husband, border collie and a few chickens.” Calls to the home in remote Trelech, Wales, went unanswered Friday.

When Masood was in school, he took his stepfather’s name, Ajao. He was athletic and popular in high school, known as someone who liked to party, according to Stuart Knight, a former classmate, who said the young man was one of only two black students in the school of 600.

“I am in shock — that is not sympathy for what he has done — he was a nice guy and I’m surprised he turned and did what he did,” Knight said.

In one of the last places Masood lived, a home in Birmingham, neighbors recalled him as a quiet man whose wife was veiled and who wore traditional Muslim clothing. But the neighborhood is not among one of the city’s many Muslim enclaves, suggesting he was not deeply embedded in its religious community.

Moazzam Begg, a former Guantanamo prisoner born and raised in Birmingham, said the details emerging of the attacker’s life raised questions about where was radicalized.

“He did not live in a Muslim neighborhood. In my mind, in my analysis, he was probably a drifter,” said Begg, adding that no one he knew in the community had met Masood. “I’d also be surprised if he had any connection with a mosque, because sadly they are places where you can no longer discuss politics or air grievances.”

Since British authorities began cracking down on mosques, many people are instead being radicalized online, Berg added.

Cultural and religious alienation can fuel such violence, he added.

Begg helps run a group called Cage that has encountered extremists who spoke of their alienation before they committed attacks. While in prison, Begg said he saw others who succumbed to radicalism. He said groups like IS can exploit people’s weaknesses and criminality.

Late Friday, the British government honored a lawmaker who battled to save the life of the police officer slain in the Parliament attack, giving him mouth-to-mouth resuscitation.

May’s office said Tobias Ellwood has been named to the Privy Council, a committee of senior lawmakers, judges and others that advises Queen Elizabeth II. The institution dates back a millennium.

Security Minister Ben Wallace, who helped coordinate the government response to Wednesday’s attack, was also named to the council.