A Somali-born student who carried out a car-and-knife attack at Ohio State University stewed over the treatment of Muslims while apparently staying under the radar of authorities, underscoring the difficulty of identifying and stopping violent lone wolves.
Abdul Razak Ali Artan was not known to FBI counterterrorism authorities before Monday's rampage, which ended with him shot to death by police and 11 people injured.
Law enforcement officials have not identified a motive for the Ohio State violence but have suggested terrorism as a possibility.
The mode of attack - ploughing a car into civilians, then slashing victims with a butcher knife - was in keeping with the recommended tactics of jihadist propaganda. And Facebook posts that were apparently written shortly before the attack and came to light afterward show Artan nursed grievances against the US.
He railed against US intervention in Muslim lands and warned, "If you want us Muslims to stop carrying lone wolf attacks, then make peace" with the Islamic State group.
"America! Stop interfering with other countries, especially the Muslim Ummah. We are not weak. We are not weak, remember that," he wrote, using the Arabic term for the world's Muslim community.
He also warned that other Muslims are in sleeper cells, "waiting for a signal. I am warning you Oh America!"
On Tuesday, a self-described Islamic State news agency called Artan "a soldier of the Islamic State" who "carried out the operation in response to calls to target citizens of international coalition countries."
Artan's social media rants seemed at odds with the portrait of the young man painted by neighbours and acquaintances.
Jack Ouham, owner of a market near the home on the outskirts of Columbus where Artan lived with his parents and siblings, saw him almost every day when he stopped in for snacks but never alcohol or cigarettes.
He was never angry, Mr Ouham said.
"Very nice guy," he said.
Artan graduated with honours from Columbus State Community College last May, earning an associate of arts degree. A video of his graduation ceremony shows him jumping and spinning on stage and smiling broadly, drawing laughs, cheers and smiles from graduates and faculty members.
He started at Ohio State in August as a business student studying logistics management.