Nine people were hurt, one critically, and Columbus Police Chief Kim Jacobs said police were looking into 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.
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.
"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.
UPDATE 1/2 : Shelter in Place lifted. Scene is now secure. ALL classes are canceled on Columbus campus for the remainder of the day.— OSU Emergency Mngmnt (@OSU_EMFP) November 28, 2016
At least two people were being treated for stab wounds, four were injured by the car and two others were being treated for cuts, university officials said.
Rachel LeMaster, who works in the engineering college, said a fire alarm sounded before the attack.
"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.
Cassidie Baker, an Ohio State senior, said she saw police or paramedics helping one person on the ground outside Watts Hall, a materials science and engineering building.
"No one really knows what is happening, other than there's an active shooter," she said.
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."
"Run, hide, fight" is standard protocol for active shooter situations. It means: Run, evacuate if possible; hide, get silently out of view; or fight, as a last resort, take action to disrupt or incapacitate the shooter if your life is in imminent danger.
The university issued a shelter in place order and an alert was sent out on social media, telling people to "run hide fight."
Buckeye Alert: Active Shooter on campus. Run Hide Fight. Watts Hall. 19th and College.— OSU Emergency Mngmnt (@OSU_EMFP) November 28, 2016
Buckeye Alert: Continue to shelter in place. Avoid area of College. More information to follow.— OSU Emergency Mngmnt (@OSU_EMFP) November 28, 2016
Facebook has activated the check-in safety feature after the incident.
FBI and ATF agents are working at the scene.
BREAKING: ATF Columbus Field Division agents are responding to scene of reported OSU active shooter.— ATF HQ (@ATFHQ) November 28, 2016
Nearly 60,000 students are enrolled at the OSU Columbus campus.
Keep checking ABC13 for the latest on this developing story.