The man killed by police on Thursday after he fatally shot nine people at a community college in southern Oregon was a nervy 26-year-old who lived close to the campus and described himself as shy, according to neighbours, media and online reports.
A law enforcement source said multiple agencies had identified the shooter as Chris Harper-Mercer. Online directories list a man of that name as having lived in Torrance, California, before moving to Winchester, Oregon.
Reuters was not able to independently verify the name of the shooter, but on Thursday night law enforcement officers were out in force at the Winchester apartment building identified in databases as Harper-Mercer's residence.
Two neighbours said they recognized online photos of Harper-Mercer as a man from the apartment building. A phone number listed for the address was busy.
The killer used four guns, including a type of assault rifle, in the classroom attack, CNN said.
Seven people were also wounded at the Umpqua Community College in Roseburg, a timber town of about 20,000 people that adjoins Winchester.
A photo posted on a MySpace profile belonging to someone named Chris Harper-Mercer, from Torrance, showed a young man with a shaved head, dark-rimmed glasses and a serious expression. He was holding a long-barreled gun.
A neighbour next door to the Winchester building said Thursday night he recognized online photos of Harper-Mercer as being his neighbour.
"I just started noticing him the last four to six months, there's a playground out behind the apartments, and we're on the second story. I go outside to smoke and I watch for anyone," said neighbour Steven Fisher, who also said he had never spoken to Harper-Mercer.
"Around 5-5:30pm in the evening I'd see him out there with a couple kids. He seemed skittish, always looking over his shoulder to see if anyone was watching," Fisher said.
Another neighbour also recognized online photos of Harper-Mercer as being a man he knew from the neighbourhood.
Many law enforcement cars, personnel and dogs had gathered at the pink apartment complex, about a four-minute drive from Umpqua Community College, by early Thursday evening.
Police tape was drawn across one of the units and officers with a dog were stationed outside. Investigators from agencies including the Douglas County Sheriff's Department, Homeland Security Protective Services and the FBI were on site.
In an Internet posting on the Spiritual Passions dating and social networking site, a user posted a picture that appears to be Harper-Mercer under the user name IRONCROSS45, a handle Harper-Mercer used as his email.
He described himself on the site as a 26-year-old, mixed-race "man looking for a woman." He said he was "not religious, but spiritual," and was a "teetotaler" living with his parents and a conservative Republican.
Socially, he said, he was "shy at first" and "better in small groups." He described himself as "always dieting" and looking for "the yin to my yang."
The same email address linked to a Chris Harper-Mercer was also associated with the profile of user Lithium_Love on torrent sharing website KickAssTorrents.
The user wrote a blog post on the site about Vester Flanagan, the man who shot dead two reporters during a live broadcast in August before killing himself, calling the footage of the shooting "good".
"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. A man who was known by no one, is now known by everyone. 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," the post said.
The user's last torrent upload was on Tuesday and was entitled "This World Surviving Sandy Hook BBC Documentary 2015," according to the website.
