An Ohio State University student plowed his car into a group of pedestrians at the college campus and began stabbing people with a butcher knife Monday before he was shot to death by a police officer.
Eleven people were hurt, one critically, and taken to local hospitals.
The attacker was identified as Ohio State student Abdul Razak Ali Artan, a Somali-born refugee who came to America in 2014 as a legal permanent resident of the United States, officials said. Police said they are investigating a motive for his attack.
Ohio State Police Chief Craig Stone said that the assailant deliberately drove over a curb outside a classroom building and then began knifing people. A campus police officer, identified as 28-year-old Alan Horujko, who happened to be nearby because of a gas leak arrived on the scene and shot Artan in less than a minute, Stone said.
Horujko has been on the police force less than two years, officials confirmed.
Those injured in the attack included an Ohio State faculty member, four graduate students and three undergrads.
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.
Police did not provide details on a possible motive, but earlier said "this was done on purpose" and would not rule out terrorism. The FBI has joined local law enforcement to investigate the attack.
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.
One student told NBC News she was walking down the street when she saw a car plow into a crowd of people who had evacuated an academic building during a fire alarm.
"This car just swerved and ran into a whole group of people," said Nicole Kreinbrink. "It hit a cop really bad."
"All these people were running and screaming and yelling," she added.
Stephen Yunker, an 18-year-old freshman at Ohio State University told MSNBC he was in his residence hall getting ready to go to class when he heard six to seven gunshots ring out. Yunker said he and his roommates soon heard sirens.
“We saw fire trucks, couple cars, and a body laying on the ground,” Yunker said.
He added that many students are shaken up and were "texting family members and friends" while the building was on lockdown.
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 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.