US investigators are piecing together evidence on why a student at a college in Oregon went on a rampage that left nine people dead before committing suicide.
Officials said the gunman, identified as 26-year-old Chris Harper Mercer, was enrolled at Umpqua Community College in Roseburg and opened fire in his English writing class.
Douglas County Sheriff John Hanlin said Mercer exchanged fire with two officers who had rushed to the scene before committing suicide.
He said 14 weapons belonging to the shooter had been recovered, including six found at the school along with a flak jacket and ammunition.
Mercer's British-born father Ian, who lives in Torrance, California, said he was devastated by the killings and didn't understand how his son managed to amass his arsenal.
"How on earth could he compile (14) guns?" he asked CNN.
"If Chris had not been able to get hold of (14) guns it would not have happened."
The shooting, the latest in a string of similar attacks in recent years at colleges and schools in the US, has revived a fierce debate on gun control.
Officials say Mercer had struggled with mental health problems for some time and left behind a typed statement several pages long in which he indicated he felt lonely and was inspired by previous mass killings.
The shooter also appeared obsessed with guns and religion and had leanings toward white supremacy.
The mother of one of the nine people injured in the carnage said her 16-year-old daughter saw Mercer single out a student and hand him an envelope before ordering the other students to move to the middle of the classroom.
"He told him 'you're going to be the lucky one' and gave him an envelope," Cheyenne Fitzgerald's mother told reporters. "He was going to be the one telling the story."
She said her daughter was shot in the back and had lost a kidney.
It was unclear how long Mercer had been a student at Umpqua, a small college of about 3,000 students located in Roseburg, a close-knit rural community.
The rampage took place on the fourth day of the new school year.
Witnesses said the gunman asked his victims their religion before shooting them execution-style.