A visibly angry President Barack Obama made an impassioned plea for gun control in the wake of the shooting, blasting Congress for its failure to act in the face of "routine" mass killings.
The unidentified man opened fire in a classroom at Umpqua Community College in rural Roseburg, and moved to other rooms methodically gunning down his victims, witnesses said.
Douglas County Sheriff John Hanlin said 10 people were killed and seven were injured, several critically. He said the identity of the victims would not be released for 24 to 48 hours.
Student Cassandra Welding was in an adjacent room when the shooting broke out.
"I probably heard a good 35 to 40 shots," Welding told US media.
She saw a fellow student be shot after opening the classroom door to see what was happening, she said.
"Then we locked the doors, turned off the lights and ... we were all pretty much in panic mode and called 911 (emergency services) and our parents and (said) 'I love yous' because we didn't know what would happen, if those were our last words."
Voicing his anger and sadness at the latest loss of life, Obama threw down the gauntlet to lawmakers - and the people who vote for them - on the thorny issue of gun control.
"Somehow this has become routine," said the president. "We become numb to this."
"We can actually do something about it, but we're going to have to change our laws," said a stony-faced Obama. "This is not something I can do myself. I have to have a Congress and state legislatures and governors who are willing to work with me on this."
"It cannot be this easy for somebody who wants to inflict harm on other people to get his or her hands on a gun," Obama said.
"Prayers are not enough," he added. "This is a political choice we make."
'Waiting for last bus'
Police were alerted to the shooting shortly after 10:30 am and rushed to the site as it was still unfolding.
"Upon arriving there, they located the shooter in one of the buildings," Hanlin said, adding that police exchanged fire with the gunman who was later confirmed dead.
It was not yet known if the shooter, identified only as a male aged 20, was a student at the college.
Authorities said investigators were examining social media postings thought to belong to him. Several reports said he may have shared his intentions online beforehand.
Other reports said police recovered a cell phone at the scene, presumably the shooter's, that contained messages linked to the massacre.
Authorities said four weapons were recovered from the scene, according to local news reports.
Police searched the entire campus after the shooting aided by sniffer dogs and patted down students and staff as they left and boarded buses that transported them to local fairgrounds.
College interim president Rita Cavin said the priority was to reunite students and staff with their loved ones.
"We have families waiting for the last bus of students to arrive and have grief counselors for those who have no children coming off the bus," she said.
"It's sad to watch the families wait for the last bus."
We all froze
Roseburg is described as a close-knit, logging community with many locals attending the college, which caters to some 3,300 students.
"Most of us have relatives taking classes here," said Douglas County fire Marshall Ray Shoufler. "Pretty much everybody knows everybody type scenario.
"So something like this affects many, many, many people."
Brady Winder, a student at Umpqua, said he was in class when suddenly he heard a loud pop coming from an adjoining classroom.
He said his teacher called out through the door to see if everything was OK and then further shots rang out.
"We all kind of froze and bolted out the door," Winder said. "I didn't really have any time to think. It was fight or flight."
School shootings are a disturbing reality of American life and many facilities have reinforced security in recent years, especially in the wake of the Sandy Hook massacre in 2012.
Twenty students and six adults were killed at the Sandy Hook Elementary School in Connecticut by 20-year-old Adam Lanza.
On Wednesday, a student who got into an argument with the principal at a high school in South Dakota pulled a gun and shot the school official in the arm before he was tackled and subdued by staff.
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