A man drove a sport utility vehicle into a crowd of pedestrians at Ohio State University then jumped out and stabbed several people with a butcher knife, injuring at least nine, before a police officer shot and killed the attacker on Monday, officials said.
A U.S. government source said investigators have reason to believe the attacker at the campus in Columbus was a Somali refugee. The city has a large Somali population.
Local officials declined to say what might have motivated the attack, and gave no details about the assailant, including his identity and whether he was a student at the university.
The attack at the Columbus campus, which was initially reported by the university on Twitter as involving an "active shooter," drew a massive response of heavily armed police.
Ohio State University police chief Craig Stone said there had been rumors of a second assailant, but police believe there was only one.
The suspect jumped the curb and used the vehicle to strike pedestrians in front of Watts Hall, Monica Moll, the university's director of public safety, said at a news conference. Local media reported the suspect used a sport utility vehicle.
He then left the vehicle armed with a butcher knife and stabbed several others, Stone told reporters.
An unidentified campus police officer who arrived at the scene shot and killed the suspect less than a minute after the attack began, Stone said.
"The only thing that you can say based upon common knowledge is that this was done on purpose," Stone said. "To go over the curb and strike pedestrians and then to get out and start striking them with a knife, that was on purpose."
One person was critically injured, a Columbus Fire Department spokeswoman said. There were differing accounts on the total number injured. The fire department reported 10, while officials at a press conference said nine.
Five victims were taken to Ohio State University Wexner Medical Center, said Dr. Andrew Thomas, the chief medical officer. They included two with stab wounds and two others who had injuries from being hit with the vehicle, Thomas said.
Two other hospitals received four patients, suffering from lacerations and injuries from being struck by the vehicle, Thomas said. None of the victims had life-threatening injuries, officials said.
CNN aired an image from a room at the university where students had barricaded a door with stacked chairs.
Columbus and university police continued their investigation with assistance from the FBI. The attack had prompted university officials to warn students on Twitter to shelter in place.
Ohio State said it had lifted the order shortly before noon EST, adding that the campus was secure.
The university campus remained open, although classes were canceled for the day.
President Barack Obama was briefed on the incident by Lisa Monaco, his homeland security adviser, said White House spokesman Josh Earnest.
"The Columbus City Council stands united with Ohio State University," said Council President Zach Klein. "We are continually thinking about and praying for all those involved and affected by this senseless act of violence."
Ohio Governor John Kasich said in a statement that state residents "thoughts and prayers go out to the Ohio State community."
(Reporting by Kim Palmer in Cleveland and Laila Kearney and Franklin Paul in New York and Mark Hosenball and Ayesha Rascoe in Washington; Writing by Alex Dobuzinskis; Editing by Jeffrey Benkoe)