ROSEBURG, Ore. - Investigators including cyber experts and hate crime specialists worked Friday to peer into the life of a 26-year-old gunman whose massacre across an Oregon campus may have been driven by religious rage and a fascination in the twisted notoriety of high-profile killers.
What is known so far about the attacker - identified by a U.S. law enforcement official as Chris Harper Mercer - appear only as loose strands that suggested an interest in firearms and the infamy gained by mass shooters. Witnesses also said he seemed to seek specific revenge against Christians.
But authorities still struggled to build a clear picture at what drove the California native to stalk rural Umpqua Community College - armed with three pistols and a semiautomatic rifle - and methodically pick off students and professors Thursday on the fourth day of the fall semester.
At the end, nine people were dead, plus Mercer, and the college joined the mournful roster of America's mass shooting sites - the 294th this year with multiple gun violence.
That night, as police picked through Mercer's apartment near campus, hundreds of people joined a candlelight vigil. Some sang along to "Amazing Grace" - the same hymn President Barack Obama offered in June when Charleston was the focus of the nation's grief and questions over another rampage.
This time, Obama said collective grief was "not enough" and made an emotional appeal for a national groundswell toward stricter gun laws.
Witnesses to the Oregon bloodshed described Mercer as questioning people at gunpoint about their religious affiliations, and appearing to single out Christians for killing.
"He said, 'Good, because you're a Christian, you're going to see God in just about one second,' " said Stacy Boylan, recounting the account of his wounded daughter, Anastasia, who underwent surgery to treat a gunshot to her spine. At least six others were wounded.
"And then he shot and killed them," he said.
Autumn Vicari, whose brother known as J.J. witnessed the shootings, told NBC News about the gruesome selection process Mercer imposed.
According to NBC: "Vicari said at one point the shooter told people to stand up before asking whether they were Christian or not. Vicari's brother told her that anyone who responded 'yes' was shot in the head. If they said 'other' or didn't answer, they were shot elsewhere in the body, usually the leg."
The violence stopped only after authorities exchanged gunfire with Mercer. At 10:47 a.m., the end was announced over the police scanner: The suspect was down.
As with many other shootings, investigators turned to the dark corners of the Web for possible clues on what pushed the attacker to move from words and images to deadly violence.
A Myspace page shows a photo believed to be Mercer sporting a crew cut and holding a rifle. The page includes posts extolling the Irish Republican Army.
Other apparent social media pages linked to Mercer point to an interest in horror films and a possible blog post on Aug. 31 about the gunman Vester Flanagan, who killed two television news employees in Virginia a week earlier while they conducted a live broadcast. Flanagan, a former employee of the station, fatally shot himself after a police chase.
"On an interesting note, I have noticed that so many people like him are all alone and unknown, yet when they spill a little blood, the whole world knows who they are," the post read, according to the Oregonian newspaper.
"A man who was known by no one, is now known by everyone," it continued. "His face splashed across every screen, his name across the lips of every person on the planet, all in the course of one day. Seems the more people you kill, the more you're in the limelight."
On another front, authorities are investigating a conversation on the message board 4chan posted Wednesday evening. The site is notorious for staging online hoaxes, in addition to cat memes, hackings and Internet attacks.
But the conversation, if authentic, appears to include a warning. "Don't go to school tomorrow if you are in the northwest," the post reads.
School shootings have figured prominently in this series of tragedies, including the 1999 massacre at Columbine High School in Colorado, the 2007 Virginia Tech shootings and the deaths of 20 children in 2012 at Sandy Hook Elementary School in Newtown, Conn.
In Washington, a visibly frustrated Obama offered prayers for the victims and their families and quickly pivoted to repeat his call for stricter gun-safety laws, something he has done throughout his presidency to no avail.
"Each time we see one of these mass shootings, our thoughts and prayers are not enough," he said. "It's not enough. It does not capture the heartache and grief and anger that we should feel. It does nothing to prevent this carnage from being inflicted someplace else in America."
Umpqua, one of 17 community colleges in Oregon, has about 2,000 students and about 200 full- and part-time faculty members. Federal data suggests Umpqua is a quiet campus; the only crimes reported there in recent years have been an occasional burglary and, in 2013, an aggravated assault.
After a 2006 incident in which one student was shot by another at Roseburg High School, local institutions - including UCC - hired security guards, according to the Eugene Register-Guard. Those security guards are unarmed, interim college President Rita Calvin told the newspaper. The campus is a gun-free zone.
Mercer grew up in California, where he attended the Switzer Learning Center for students with disabilities. Rick Rada, a former classmate, recalled Mercer as quiet, cheerful and nonviolent.
"To me Chris was just an ordinary guy, really. He was one of the silent types like me," Rada told The Washington Post. "But we got along with our teachers. He opened up with the teachers, talked to them, had fun."
Former neighbors in Torrance, Calif., a beach-side city just south of Los Angeles, told the Los Angeles Times that Mercer liked to practice target shooting and tended to act "anxious or nervous," as Rosario Espinoza put it.
He and his mother, Laurel Harper, mostly kept to themselves, except for occasional disputes over bugs or loud noises. Espinoza's mother, Rosario Lucumi, recalled thinking it "strange" that Harper referred to her son as "baby."
Mercer moved to Oregon with his mother a year or two ago, according to public records. It's not clear if and how he may have been affiliated with Umpqua Community College, though a student told CNN that she took a theater class with Mercer, and a "Chris Harper-Mercer" is listed as a production assistant on the Facebook page of a UCC fall show.
His father, Ian Harper, still lives in Los Angeles. Harper stepped outside his home there briefly on Thursday night to say that he'd spent the day speaking with law enforcement and couldn't answer questions about his son or the shooting.
"Shocked is all I can say," he told reporters. "It's been a devastating day."
Gloria Buhring, a neighbor at the Winchester apartment complex where Mercer appeared to have lived, said police officers swarmed the area Thursday, blocking much of the complex off with police tape.
Buhring didn't know Mercer. But on Wednesday, she returned home to find a previously empty trash container "overflowing with stuff that looked like it had been moved from an apartment," she told The Washington Post. "It looked like somebody had gotten rid of a lot of stuff and left."
Another Winchester neighbor, Bronte Hart, told Seattle TV station KIRO that Mercer would "sit by himself in the dark in the balcony with this little light."
Hart said a woman she believed to be Mercer's mother lived with him and was "crying her eyes out" Thursday.
Steven Fisher, who also lives nearby, described Mercer as "skittish."
"His demeanor, the way he moved, always looking around," Fisher said. "I got a bad vibe from him."
The violence started just after 10:30 a.m., when students in Snyder Hall - a modest building in the southeast part of campus where science and English classes are held - heard a sudden popping noise.
Some were bewildered by the noises. But Sarah Cobb, a 17-year-old who heard the sound from her Writing 121 class in Snyder, recognized them immediately.
"I grew up hunting, so by then I knew what it was," she told The Washington Post. Cobb screamed to her teacher that they all needed to get out, and the instructor opened the door into chaos: students running, a teacher crying, a man screaming for someone to call 9-1-1. Cobb left her phone, her backpack and all of her belongings in the classroom, and then ran out of the building, tripping her way down the stairs.
"There was so much screaming you knew it was serious," she said. "I was terrified. I was sprinting. You could hear the gunshots echoing in the hall."
In a room nearby, Cassandra Welding heard the percussive sounds of gunshots with horror. A classmate opened the door to look at what was happening, Welding told the LA Times, and was shot.
"We were screaming, 'Close the door! Close the door!' " Welding said.
Someone dragged the injured woman back into the room and locked the door. Taking turns, classmates performed CPR on the woman, who had been shot in the torso. Her broken glasses lay on the floor near her, Welding told the LA Times. Blood was splattered on the walls.
The students crawled toward the back of the room, away from the door.
"I was so terrified for my life and I was shaking," Welding said. While another classmate called 9-1-1, the 20-year-old phoned her mother. She wasn't the only one.
"I just heard other people in tears, crying, calling their loved ones and telling them, 'I love you.' " she told the Times. "It was such a heart-wrenching thing."
The UCC campus will remain closed Friday, as officials continue to catalogue and investigate the aftermath. Around Oregon, flags are being flown at half-staff.
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Hoyt is a freelance writer. Brian Murphy, Mark Berman, Susan Svrluga, Abby Phillip, Ellen Nakashima, Darryl Fears and Nick Anderson in Washington contributed to this report.