No evidence has emerged that Mr. Artan had any connection or allegiance to radical ideology. Though no terrorist group had claimed responsibility for the attack, the Islamic State was updating its online audiences on the rampage on Monday.

Both the car-ramming and the knife attacks are now established forms of aggression inspired by the Islamic State. An attacker in Nice, France, used a delivery truck to kill dozens of pedestrians in July, and chats between an attacker in Würzburg, Germany, and his Islamic State handler indicate he was initially told to use a car to carry out his assault that same month, before he settled on using an ax because he did not have a driving permit.

The authorities in Ohio said that it was too soon to know what had motivated Mr. Artan, but that it was clear the attack had been deliberate. Mr. Artan’s Columbus home was surrounded by squad cars, crime scene tape and a bomb squad truck on Monday afternoon, and police officials said they were waiting for a search warrant.

“This was done on purpose,” said Chief Craig Stone of the Ohio State University police. “To go over the curb and strike pedestrians and then get out and start striking with the knife — that was on purpose.”

The attack, initially reported as an “active shooter” by the university, stunned students who were returning to class after Thanksgiving break, leading to a 90-minute shelter-in-place warning and an admonition from campus officials to “Run Hide Fight.”