The attacker, identified by police as a Ohio State University student, drove his car into a group of people before stabbing bystanders with a knife.
Eleven people were injured when a student rammed his car into a crowd at the Ohio State University (OSU) before attacking bystanders with a knife.
The attacker, identified by officials as OSU student Abdul Razak Ali Artan, was shot and killed by a campus police officer. According to the Columbus city fire officials, one person injured in Monday's attack was in critical condition.
Two US government sources, who could not speak on the record because of the ongoing investigation, said the assailant was an immigrant from Somalia and a permanent resident of the United States.
"We can tell you the suspect is an OSU student," Craig Stone, police chief at the university, told a news conference at which officials released the name of the suspect.
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 Police (@OSUPOLICE) November 28, 2016
UPDATE: Police continue to process scene. Avoid area between College & Neil, Glenn & Woodruff. Lane Ave.Garage and SAS building remain close— OSU Police (@OSUPOLICE) November 28, 2016
Ohio Governor John Kasich also made a statement.
Ohio's thoughts and prayers go out to the Ohio State community. Be safe, listen to first responders. https://t.co/5qtfH3Fb6d— John Kasich (@JohnKasich) November 28, 2016
US Representative Adam Schiff, the ranking Democrat on the House Permanent Select Committee on Intelligence, said intelligence agencies were assisting in the investigation.
"It bears all of the hallmarks of a terror attack carried out by someone who may have been self-radicalized," Schiff said in a statement.
Another US official, who asked not to be named because of the ongoing investigation, told Reuters that US agencies are investigating the Columbus attacker's background and motivations, but cannot clearly say yet whether he had any ties to suspected militant cells or groups.
Ohio State University sent a series of tweets Monday morning warning of an active shooter on campus, telling students to shelter in place and 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. Wait for Police officers directions. Please contact Police / 9-1-1 only if you have information— OSU Emergency Mngmnt (@OSU_EMFP) November 28, 2016
Ohio State president Michael Drake cautioned against jumping to conclusions when asked about a possible connection to the Somali community.
"We all know when things like this happen that there's a tendency sometimes for people to put people together and create other kinds of theories," he told a news conference.
"We don't know anything that would link this to any community. We certainly don't have any evidence that would say that's the case," Drake added.
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
Monday's attack unfolded just before 10:00 am (1500 GMT), when police were alerted that a car had struck pedestrians on campus.
The whole incident lasted just a few minutes but triggered a tense lockdown on the university's main campus in Columbus, with panicked students hiding in bathrooms before the scene was declared secure.
"Everybody was running in any direction they possibly could, students were running out of the classroom building," she said from her hiding spot in a locked bathroom.
Ohio State has roughly 60,000 students on the main campus in Columbus, which sprawls across more than 1,900 acres (770 hectares).
A number of vigils and gatherings were planned, as university officials offered student and staff counseling.