The killer burst into Umpqua Community College in Roseburg and opened fire. Eye-witnesses say he was asking victims their religion before shooting people who identified themselves as Christian.
The 26-year-old was later killed in a shootout with police.
Dad Ian Mercer told reporters outside his home he is 'as surprised as anyone' at the tragedy.
He said: "Obviously, it's been a devastating day. Devastating for me and my family.
"I'm just as shocked as everybody at what happened today. I've just been talking to the police and the FBI. That's all the details I have right now, is what you know already."Police recovered four weapons at the scene, including three handguns and a long-range rifle, according to reports.
