COLUMBUS, Ohio — A Somali-born Ohio State University student plowed his car into a group of pedestrians on campus and then got out and began stabbing people with a butcher knife Monday before he was shot to death by a police officer. Police said they were investigating whether it was a terrorist attack.

Eleven people were hurt, one critically.

The attacker, Abdul Razak Ali Artan, was born in Somalia and was a legal permanent U.S. resident, according to a U.S. official who

wasn’t authorized to discuss the case and spoke on the condition of anonymity. The FBI joined the investigation.

The details emerged after a morning of conflicting reports and confusion, created in part by a series of tweets from the university warning there was an “active shooter” on campus and students should “Run Hide Fight.” The warning was prompted by what turned out to be police gunfire.

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, before getting the all-clear an hour and a half later.

Ohio State University police Chief Craig Stone said the assailant deliberately drove his small Honda over a curb outside an engineering classroom building and then began knifing people. A campus officer 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 Watts Hall 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 the man didn’t say anything when he got out.

Mary Greenberg of Naperville was alerted to the attack by a text message from her son, Nick, who is a freshman at Ohio State, she told ABC 7 Chicago.

“He sent me the Buckeye alert that said there was an emergency situation, more information coming soon,” Greenberg said. “And then it said ‘active shooter on campus,’ and then he texted and said, ‘Someone got shot right where I was. Cops are everywhere. I’m in my dorm.’”

The texts continued for several hours as the situation unfolded.

“He doesn’t have access to the news in his room, so, I don’t know, we were sort of keeping him up to date and he was sort of looking out the window. He’s right there, very close to where it all happened,” she said.

In Woodridge, Bobbi Diedrick first saw the news on Facebook and thought immediately of her son Mike, a junior at Ohio State.

“I wasn’t sure where he was,” she told ABC 7. But he was across campus, nowhere near the attack.

“It’s pretty scary, I’m not even going to lie,” Mike Diedrick told ABC 7 while the campus was still on lockdown. “I’m not being affected by it right now because I’m not near what’s going on, but knowing that the suspect is still out on the loose makes it all that bit more on edge.”

Most of the injured were hurt by the car, and at least two were stabbed. One had a fractured skull.

Columbus police Chief Kim Jacobs, asked whether authorities were considering the possibility it was a terrorist act, said: “I think we have to consider that it is.”

• ABC 7 contributed to this report.