Federal and local investigators believe the attack launched earlier this week at Ohio State University involved only Abdul Razak Ali Artan, who was likely inspired by slain al-Qaeda operative Anwar al-Awlaki and anti-U.S. rhetoric spewed by the Islamic State.

Angela Byers, chief of the FBI's Cincinnati Division, also said Wednesday that Artan was not known to law enforcement authorities prior to Monday's assault in which the 18-year-old man crashed a car into a campus crowd and then lashed out with a butcher knife before he was fatally shot by a campus police officer.

"He was not the subject of any investigation,'' Byers said in a briefing on the ongoing investigation.

Eleven people were injured in the attack.

"All we know is that we believe (Artan) may have been inspired by Anwar al-Awlaki and ISIL,'' Byers said.

As part of Wednesday's update, Byers appealed for public assistance in establishing Artan's whereabouts in the hours before the 9:52 a.m. assault, and when he purchased a knife in a Columbus-area Wal-Mart earlier that day.

Authorities said it was not yet known whether the knife Artan purchased Monday was the one used in the attack.