ST. CLOUD, Minn. — The man who stabbed 10 people at a Minnesota mall had become interested in Islam in the last several months, withdrew from his friends, and encouraged female relatives to be more religious, the FBI said Thursday.

“We were told (he) had not previously shown an interest in religion,” but after 20-year-old Dahir Ahmed Adan did, he went from being a high academic performer to failing out of college “almost overnight,” Minneapolis FBI Special Agent in Charge Rick Thornton said at a news conference in which authorities gave the public its first look at surveillance video of some of the Sept. 17 attacks.

The attorney for Adan’s family, Abdulwahid Osman, said his parents and close family members did not see the behavioral changes that investigators described. “They believed he was doing as good as he used to do,” Osman said. “That is not the son they knew.”

Witnesses told the FBI that Adan, who was armed with two steak knives and was later shot and killed, referenced Islam during the attack at Crossroads Center mall. “We have numerous credible witness accounts of him asking victims during the attack if they were Muslim and at least one instance yelling ‘Allahu akbar’ while stabbing one of his victims and others heard him yelling “Islam Islam” during the attack,” Thornton said, adding that it appeared to be premeditated.

Aside from Adan’s supposed increased interest in the religion, Thornton offered no other evidence linking Adan, who was Somali-American, to extremist groups.

Right after the attacks, an Islamic State-run news agency claimed Adan was a “soldier of the Islamic State” who had heeded the group’s calls for attacks in countries that are part of a U.S.-led anti-IS coalition.