Columbus, Nov 29: A Somali-born college student plowed his car into a group of pedestrians at Ohio State University and began stabbing people with a butcher knife before he was shot to death by a police officer.
Police said they are investigating whether it was a terrorist attack.
Eleven people were hurt, one critically. The attacker was identified as Ohio State student Abdul Razak Ali Artan.
He was born in Somalia and was a legal permanent resident of the US, according to a US official who wasn't authorised to discuss the case and spoke on condition of anonymity.
The FBI joined the investigation.
The details emerged after a morning of confusion and conflicting reports that began with the university issuing a series of tweets warning that there was an "active shooter" on campus near the engineering building and that students should "run, hide, fight."
The warning was apparently prompted by what turned out to be police gunfire.
Numerous police vehicles and ambulances converged on the 60,000-student campus, and authorities blocked off roads.
Students barricaded themselves inside offices and classrooms, piling chairs and desks in front of doors.
Ohio State Police Chief Craig Stone said that the assailant deliberately drove over a curb outside a classroom building and then got out and began attacking people with the knife.
A campus officer who happened to be nearby because of a gas leak arrived on the scene and shot the driver in less than a minute, Stone said.
Angshuman Kapil, a graduate student, was outside the building when the car barreled onto the sidewalk.
"It just hit everybody who was in front," he said.
"After that everybody was shouting, 'Run! Run! Run!'"
Student Martin Schneider said he heard the car's engine revving.
"I thought it was an accident initially until I saw the guy come out with a knife," Schneider said, adding that the man didn't say anything when he got out.
Most of the injured were hurt by the car, and at least two were stabbed, officials said.
One had a fractured skull. Asked at a news conference whether authorities were considering the possibility it was a terrorist act, Columbus Police Chief Kim Jacobs said: "I think we have to consider that it is."
Surveillance photos showed Artan in the car by himself just before the attack, but investigators were looking into whether anyone else was involved, the campus police chief said.
In recent months, federal law enforcement officials have raised concerns about online extremist propaganda that encourages knife and car attacks, which are easier to pull off than bombings.
The Islamic State group has urged sympathisers online to carry out attacks in their home countries with whatever weapons are available to them.