PHOTOS: Deadly campus shooting at community college in Oregon
"Shocked," he said. "Shocked is all I can say, okay? Obviously, it's been a devastating day. Devastating for me and my family, so all I ask is, I know you guys are here to do your job, all I ask is would you please respect our privacy. And so far you've done that."
Neighbors say the gunman lived in Torrance for a time.
Former neighbor David Westly said, "I did see him at the time leaving his apartment and coming home with what looked like gun cases, him and his mom both. And he actually did say he used to go shooting at some range, I don't know where it was, but that's all I know."
Mercer's father says he's cooperating with investigators.
VIDEO: Oregon community torn apart by community college shooting
At a press conference Thursday evening, the Douglas County Sheriff John Hanlin said he knew who the shooter is, but wouldn't confirm it.
"I will not name the shooter. I will not give him the credit he probably sought prior to this horrific and cowardly act," Hanlin said.
Oregon Gov. Kate Brown said the gunman was a student at the college.
Investigators recovered four weapons from the scene, three pistols and a rifle. Investigators are also searching homes of relatives. His mother lives in Roseburg. Some reports say the shooter had body armor.
A student who witnessed her teacher's murder told the local newspaper: "The shooter was asking people to stand up and state their religion and then started firing away."
Law enforcement are pouring over threatening posts made Wednesday on an online bulletin board. It said, in part, "Don't go to school tomorrow if you are in the northwest."
VIDEO: Oregon community college shooting stirs gun control debate
Hannah Miles, a 19-year-old freshman at the community college, says she was in a writing class when her teacher got a call from security saying the school was on lockdown.
She says she heard gunshots from a neighboring classroom and her teacher and fellow students huddled together in their locked classroom. Miles says they heard footsteps outside, and a man's voice call out to them, "Come on out, come on out." They remained quiet and didn't open the door.
She says police soon arrived and after students were convinced they were indeed officers, they opened the door. Miles says seeing the officers was "like a huge burden had been lifted."
Mercer's neighbor, Bronte Harte, said he "seemed really unfriendly."
Harte lived below Mercer in an apartment complex in the community of Winchester. She says Mercer would "sit by himself in the dark on the balcony with this little light."
She said a woman she believed to be Mercer's mother also lived upstairs and was "crying her eyes out" Thursday.
One of the three heroes from Sacramento who stopped a terrorist attack on a train in Europe said he attended Umpqua Community College. Alek Skarlatos studied law enforcement there and is headed to Roseburg there. He said, "I wish I could have been there today to assist." Skarlatos will be on Good Morning America Friday morning starting at 7 a.m.
ABC7 News reporter Wayne Freedman is in Roseburg. You can see his reports during our evening newscasts or follow him on Twitter and Facebook for the latest updates.
Click here for full coverage on the Oregon college shooting shooting.
The Associated Press contributed to this report.
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