COLUMBUS, Ohio (KDKA/AP) — A man plowed his car into a group of pedestrians at Ohio State University and then got out and began stabbing people with a butcher knife before he was shot and killed by an officer Monday morning, campus police said.

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 U.S., according to a U.S. official who wasn’t authorized to discuss the case and spoke on condition of anonymity.

The officer who shot and killed Artan was identified as Officer Alan Horujko.

Eleven people were hurt, one critically, and Columbus Police Chief Kim Jacobs said police were investigating whether it was a terrorist attack.

The details emerged after a morning of confusion and conflicting reports that began with the university issuing a series of tweets warning students that there was an “active shooter” on campus near the engineering building and that they should “run, hide, fight.”

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

Ohio State Police Chief Craig Stone said that the attacker drove over a curb outside a classroom building and that an officer who was nearby shot the driver.

There's at least one body bag present in front of Koffolt Labs. OSU police still advising to take shelter. Situation not under control. pic.twitter.com/fIdvjpwbzD — The Lantern (@TheLantern) November 28, 2016

“The threat ended when the officer shot the suspect,” said Monica Moll, the school’s public safety director.

The shelter-in-place warning was lifted about an hour and half later and the campus was declared secure after police concluded there was no second attacker, as rumored.

A student from Latrobe said she was in class right next to the building where the attack took place.

“All we did was stay where we were at and lock the doors of the building. We didn’t really know what to do because it was so close, we didn’t want to go outside,” said Megan Ratallick of Latrobe.

“It was so out of the blue, and it was just unnerving knowing it could happen anywhere at anytime, and you never expect it to happen on your campus,” said Andrew Lancio of Pine Township.

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.

Ohio State’s student newspaper, The Lantern, ran an interview in August with a student named Abdul Razak Artan, who identified himself as a Muslim and a third-year logistics management student who had just transferred from Columbus State in the fall.

He said he was looking for a place to pray openly and worried about how he would be received.

“I was kind of scared with everything going on in the media. I’m a Muslim, it’s not what media portrays me to be,” he told the newspaper. “If people look at me, a Muslim praying, I don’t know what they’re going to think, what’s going to happen. But I don’t blame them. It’s the media that put that picture in their heads.”

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 sympathizers online to carry out attacks in their home countries with whatever weapons are available to them.

In September, a 20-year-old Somali-American stabbed 10 people at a St. Cloud, Minnesota, shopping mall before being shot to death by an off-duty officer. Authorities said he asked some of his victims if they were Muslim. In the past few years, London and other cities abroad have also seen knife attacks blamed on extremists.

The shelter-in-place warning at Ohio State was lifted and the campus declared secure after police concluded there was no second attacker as rumored.

The bloodshed came as students were returning to classes following the Thanksgiving break and Ohio State’s football victory over rival Michigan that brought more than 100,000 fans to campus on Saturday.

Rachel LeMaster, who works in the engineering college, said a fire alarm sounded on campus during the emergency.

“There were several moments of chaos,” she said. “We barricaded ourselves like we’re supposed to since it was right outside our door and just hunkered down.”

LeMaster said she and others were eventually led outside the building and she saw a body on the ground.

Classes were canceled for the rest of the day.

The officer who gunned the attacker down was identified as 28-year-old Alan Horujko, a nearly two-year member of the force.

The initial tweet from the university’s emergency management department went out around 10 a.m. and said: “Buckeye Alert: Active Shooter on campus. Run Hide Fight. Watts Hall. 19th and College.”

Ohio State President Michael Drake said the active-shooter warning was issued after shots were heard on campus.

“Run, hide, fight” is standard protocol for active shooter situations. It means: Run, evacuate if possible; hide, get silently out of view; or fight, take action to disrupt or incapacitate the shooter if your life is in imminent danger.

(TM and © Copyright 2016 CBS Radio Inc. and its relevant subsidiaries. CBS RADIO and EYE Logo TM and Copyright 2016 CBS Broadcasting Inc. Used under license. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed. The Associated Press contributed to this report.)