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,” FBI Special Agent Rick Thornton said at a news conference. He also noted 20-year-old Dahir Ahmed Adan went from being a high academic performer to failing out of college “almost overnight” after taking an increased interest in Islam.

During the Sept. 17 attack, which started outside of Crossroads Center mall before moving inside, witnesses told the FBI that Adan referenced Islam.

“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.

Aside from Adan’s supposed increased interest in the religion, Thornton offered no other evidence of any links to extremist groups, including the Islamic State group. He said investigators are still working on Adan’s digital footprint, including social media accounts, and haven’t yet unlocked his iPhone. He said investigators are assessing “legal and technical options” for the phone.

FBI Director James Comey said last week it appeared Adan, who is Somali, was at least partly inspired by extremist ideology. When the attacks happened, the 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. It wasn’t immediately known whether the extremist group had planned the attack or knew about it beforehand.

Stearns County Attorney Janelle Kendall said Adan was armed with two steak knives. The off-duty officer from a nearby city who shot Adan six times and killed him inside a Macy’s store won’t face charges, said Kendall, who showed surveillance video of Adan crawling and trying to get up after being shot.

While testifying before the House Judiciary Committee last week, Comey said the FBI was still working on the case and reviewing Adan’s electronic devices, but it appeared Adan was motivated “by some sort of inspiration from radical Islamic groups.”

Minnesota has the nation’s largest Somali community, with census numbers placing the population at about 57,000. Young Somalis have been a target for terror recruiters. Since 2007, more than 20 young men have joined the militant group al-Shabab in Somalia. In addition, roughly a dozen people have left to join militants in Syria, and nine Minnesota men face sentencing on terror charges for plotting to join the Islamic State group.

(AP)