A portrait has begun to emerge of the gunman behind America's latest mass shooting, but police say there are few clues to the motive for the carnage unleashed at a college in Oregon.
The rampage on Thursday (local time) by a heavily armed young man identified as Chris Harper Mercer, 26, left 10 dead and shattered a close-knit rural community in the south of the state.
The bloodshed in Oregon prompted an impassioned new plea for gun control by President Barack Obama, who said Americans had become "numb" to the horror of mass shootings.
Hospital officials updated the number injured from seven to 10. The fatalities include the shooter.
Mercer's motive remained unclear.
Police have gone to the youth's home and are canvassing neighbourhoods door-to-door as they investigate, Douglas County Sheriff John Hanlin told CNN on Friday.
But he said it was too early to talk about why the shooter entered Umpqua Community College and methodically gunned people down one after another.
Hanlin pointedly would not call him by his name. "I don't want to glorify the shooter," he said. "You won't hear his name from me or from this investigation."
As investigators worked to put together a fuller picture of Mercer, the New York Times quoted an unnamed law enforcement official as saying, "He appears to be an angry young man who was very filled with hate."
One man whose daughter was wounded told CNN that the gunman ordered students to say if they were Christian or not.
"They would stand up and he said 'Good, because you're a Christian, you're going to see God in just about one second'," Stacy Boylan told CNN, relaying his daughter Ana's account. She survived by playing dead.
Mercer's father Ian, reached by reporters in Los Angeles, would only say he was shocked and devastated and asked to be left alone.
An online dating profile attributed to Mercer, however, describes him as "Not Religious, Not Religious, but Spiritual."
A photo with the profile shows a man with a shaved head, medium build and wearing a grey tank top shirt. The profile says he is mixed race.
In the personality section, he is depicted as "lover, conservative, professional, intellectual, introvert."
Derrick McClendon, a former neighbour of Mercer when he lived in Torrance in southern California, said the young man was so withdrawn and ill at ease that he would ask sometimes ask if everything was OK, the Times reported.
"I would say, 'Hey, man, you all right?'" McClendon said. "He would say 'hi,' but that's it. He was really shy," the Times quoted McClendon as saying.
Neighbours described Mercer as a withdrawn, anxious man who lived with his mother.
They told the Times he wore the same outfit every day - combat boots, green army pants and a white T-shirt.