The gunman, 26, opened fire at Umpqua Community College on Thursday morning and was killed in a police shootout.
There were conflicting reports on casualties but Douglas County Sheriff John Hanlin said 10 dead, including the gunman, was “the best” figure.
Police have not identified the attacker but unnamed officers have told US media his name is Chris Harper Mercer.
Mr Hanlin said he would not confirm the name, adding: “I will not give him the credit he probably sought prior to this horrific and cowardly act.”
The gunman was reportedly born in the UK and moved to the US as a young boy.
A man identified as the gunman’s father, Ian Mercer, told US media he was “just as shocked as everybody” by his son’s actions.
The killer’s motive is not known, although police said they were investigating reports that he had warned of his intentions on social media.
Hours after the attack, in which seven were also injured, a visibly frustrated President Barack Obama demanded tighter gun laws, saying prayers are “no longer enough”.
Such shootings – and his own response – had become routine, he said, barely concealing his exasperation.
“We are not the only country on Earth that has people with mental illnesses or want to do harm to other people.
“But we are the only advanced country on Earth that sees these mass shootings every few months.”
Lorie Andrews, who lives opposite the campus, said she heard what sounded like fireworks and when she came out of her home she saw students streaming out.
“One girl came out wrapped in a blanket with blood on her,” she said.
Hannah Miles, 19, said that she and fellow students were led to a nearby bookshop, where they hid in a back room.
“No-one really was sure what was going on,” she said. “The next thing we knew, there were three or four more gun shots and everybody just looked at each other – and we knew.”
Stacy Boylan, the father of a woman who survived the shooting, told CNN that his daughter had described how the gunman asked his victims to state their religion before opening fire.
According to Mr Boylan, his daughter said the gunman told the Christians he killed that they were about “going to see God in just about one second”.
Another student who survived the shooting, Kortney Moore, gave a similar account to a local newspaper, The News-Review.
The 3,000-student school is located in Roseburg, Oregon, a rural area about 175 miles (280 km) south of Portland.
Hundreds of people gathered for a vigil in a Roseburg park in the evening.
The suspect supposedly used a “long gun”.
Students were transported by bus to a local fairground to be reunited with their loved ones.
According to Umpqua Community College’s website, the average age of students is about 38.