COLUMBUS, Ohio -- The Ohio State University campus has been cleared and the suspect behind Monday's violent attack has been killed by police, leaving many unanswered questions.

Here's what we do know about the suspect:

According to NBC News, the suspect has been identified as 18-year-old Abdul Razak Ali Artan. Artan was an Ohio State student and Somali refugee. He left his homeland with his family for Pakistan in 2007. In 2014, he became a permanent U.S. citizen, NBC News reports.

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The outlet also reports, investigators are looking at whether Artan was inspired by overseas terrorist propaganda.

Both ISIS and al Qaeda have urged followers to carry out attacks with vehicles or knives.

Just two months ago, ISIS claimed credit for a knife attack that hurt nine people at a Minnesota shopping mall.

French police say a truck attack in July that killed 84 people in Nice was inspired by ISIS.

OSU campus police say they're confident Artan came to the campus alone and carried out the attack by himself. Now they're investigating whether anyone else was involved in planning it.

Artan allegedly drove a vehicle into a crowd of students after Watts Hall was evacuated due to a fire alarm. Witnesses say he jumped out of the car and began slashing and stabbing people with a large butcher knife before he was shot and killed by police.

Nine students were hospitalized, but none suffered life-threatening injuries, according to the Associated Press.

Artan's motive remains unclear, but officials tell NBC News that the attack was intentional and possibly pre-meditated.