ROSEBURG, Ore. >> Twenty-year-old Marc Beckwith was in Room 16 of low-slung, mansard-roofed Snyder Hall, preparing for his computer lab. Cassandra Welding, also 20, was slipping into the lab room just as a familiar figure was slipping out.

It was Lawrence Levine, low-key, bearded, grizzled, on his way to teach a writing class next door in Room 15. Welding had taken the class, and treasured his patient encouragement. "I said, ‘Oh, hi, Larry,’" she recalled in an interview.

The classes began at 10 a.m. By shortly after 10:30, Levine, 67, was dead of a gunshot wound to the head.

Thursday, cool and cloudy, was the fourth day of classes at Umpqua Community College here. Planted in a hairpin bend of southwest Oregon’s North Umpqua River, the tree-studded campus seemed to embody what the college’s website promised: "a peaceful, safe atmosphere" for aspiring scholars of any age to pursue their dreams.

But it was not. Levine was among the first people whom 26-year-old Christopher Harper-Mercer, a student in his class, shot to death. He would kill eight more — a 20-year-old forward on the school basketball squad, a 34-year-old outdoorsman out to improve his mind, a 59-year-old British expatriate attending college with her daughter, and others — before police officers arrived and wounded him in an exchange of gunfire. Nine others were wounded.

Harper-Mercer died of a self-inflicted gunshot wound, officials said Saturday.

"I heard one shot and said, ‘We need to get out.’ Then I heard a second and third, and I ran," said Sarah Cobb, a 17-year-old first-year student who was in a writing classroom next to Levine’s. "I was sprinting. I never ran so fast in my life.

"I kept my head when I was running away from the scene, but when I was in lockdown I broke down," she said.

The minutes Harper-Mercer needed for his grisly work were an eternity for the scores of students and instructors in Snyder Hall. The carnage was mostly limited to Levine’s classroom, where almost all of the occupants apparently were either killed or wounded. But in other classrooms, scenes of terror, panic and heroism played out as students crawled into hiding, cared for the wounded and, in one case, stood off the gunman as he sought to enter.

Roseburg now joins Charleston, South Carolina; Newtown, Connecticut; Blacksburg, Virginia; Aurora, Colorado, and many more on the roster of places where troubled men with firearms — almost uniformly men — have uncorked their rage through mass killings.

Like some of them, Harper-Mercer was deeply involved with firearms and had a small armory during his Snyder Hall rampage: body armor, five handguns, a semi-automatic rifle and several magazines of ammunition. Like virtually all, he smoldered with real or imagined grievances in a life that seemed off-kilter to others, and pointless to himself, investigators say.

Described by neighbors as terse and morose, Harper-Mercer lived with his mother, who divorced his father when their son was about 16. Harper-Mercer had a brief and failed stint in Army basic training in 2008 and graduated from a California high school for students with learning disabilities the next year. At home, he inveighed against noisy neighbors, barking dogs, roach-infested rooms, organized religion and, shortly before the killings, an existence devoid of girlfriends and sex.

Roseburg held the prospect of a better life. Harper-Mercer and his mother, Laurel Harper, moved there from a one-bedroom apartment in Torrance, California, after she found a nursing job. "It was what she was looking for, peace and quiet, no city life. They were up there to start over again," Louie Flores, 32, a neighbor in Torrance, said in an interview. "Chris, that was the first time I had actually seen him happy, to be honest. I’d always seen him just straight-faced. He was excited to get out of LA as well, to be out there. He said: ‘I like the woods. I like being in the woods.’"

When Levine convened his writing class in Snyder Hall on Thursday morning, Harper-Mercer was apparently not in his seat. When he did appear roughly a half-hour later, descriptions of what happened vary. Some say he fired through a window, striking Levine in the head, even before barging through a classroom door from a parking lot.

A graphic but unverified account by relatives of one injured student, Anastasia Boylan, differed. Harper-Mercer stormed into the room, they said in an interview with CNN, and said to Levine, "I’ve been waiting to do this for years." Then he shot him.

The instructor in the computer lab next door, where Welding and Beckwith were, had left on a brief errand. The students know only that they heard a loud pop — like a book being dropped on the floor — and, perhaps 10 seconds later, a scream and a man’s voice.

"I think it was someone saying, ‘Oh, my God,’" Beckwith said.

A pause. A second shot, a third, a fourth and a cacophony of screams. In the lab, Beckwith said, one older student, a woman with graying hair and a cane, went to a door that, like others in the building, opened to the exterior, not a hallway, and stepped out. "I’m going to go check on them," he recalled her saying.

Seconds later, she returned and collapsed into his arms. Her chest was bloody, and part of her right arm had been ripped away. "Don’t go out there," he said she had told him. "It’s not safe."

Beckwith said he did anyway, racing across the parking lot to a nearby house to summon help. At 10:38, the Douglas County Sheriff’s Department received a call from the campus. Seconds later, a dispatcher asked for medical aid at Snyder Hall.

"Somebody is outside one of the doors shooting through the door," the dispatcher said. "There is a female in the computer lab. We do have one female that has been shot."

Patrol cars were racing to campus, asking where Snyder Hall was. "We are looking up location on a map," the dispatcher radioed, some 2 1/2 minutes after the initial call for help.

More than a minute later: "There’s approximately 35 people in Snyder Hall right now in the classrooms."

In the adjacent rooms, panic reigned. In the computer lab, Welding said, the woman who had been shot, gasping for air, was dragged inside and given CPR. As others shouted "Close the door!" someone shut off the lights. With gunshots popping from Room 15, the students barricaded themselves in a corner with desks and backpacks.

Across the wall from Levine’s classroom, Hannah Miles, 19, was in a writing class when the shots erupted. Students suggested that the instructor open a sliding door connecting the two classes to see what was happening. "I’m not going to open that door," Miles quoted the teacher as saying, but she did knock and ask whether all was well.

The response was a staccato series of shots. "Everybody out," someone yelled, and the classroom emptied chaotically into the outdoors, students running to other buildings to hide.

Thirty-year-old Chris Mintz, an Army veteran who was studying fitness training at Umpqua, saw the gunman. According to family and friends, he blocked a classroom door as Harper-Mercer tried to enter.

The gunman shot him repeatedly through the doorway, then pushed through. Mintz, on the floor, told his attacker that it was his son’s sixth birthday, and was shot again before the gunman moved on. Mintz is expected to recover from his wounds.

Barely six minutes after a police dispatcher raised the first alarm, an officer who had arrived on campus radioed a message: "We’re exchanging shots with him. He’s in a classroom on the southeast side of Snyder Hall."

Two minutes later, another messages crackled over the radio: "Code Four," the officer said, signaling that no more help was needed. "The suspect is down."

And then two minutes after that: "We’ve got multiple gunshot wounds. We’re going to need multiple ambulances on scene."