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 today.

“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 totality of Dahir Adan’s behavior and the actions suggest he may have been radicalized either with the influence of others or on his own,” Thornton said.

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 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.

Thornton also said investigators are looking at Adan’s digital footprint, including social media accounts, and are assessing “legal and technical options” to unlock his iPhone. He didn’t elaborate, and agency spokesman Kyle Loven said he couldn’t comment further because of the ongoing investigation.

The FBI hired an outside company to help it hack into an iPhone used by one of the San Bernardino, California, shooters, Syed Rizwan Farook, who with his wife killed 14 people at a 2015 holiday work gathering. Apple had rejected the government’s demand that it create software to bypass the phone’s security features. The FBI has refused to name the company that developed the tool or say how much it paid for it.

The mall videos shown at the news conference showed Adan swinging wildly at an electronics store clerk and stabbing him at least once before the man scrambled away, as well as customers running from a candy store and the store’s clerk pulling down a barrier just as Adan approached.

Another graphic video showed a bloody Adan crawling and trying to get up after he was shot six times by an off-duty officer.

Law enforcement shared the videos with the family today, Osman said.

“They continue to mourn and grieve for the loss in their family and express profound sympathy to the victims,” he said.

In arguing that it appeared the attack was premeditated, Thornton said compelling evidence included Adan not changing out of his security guard uniform between shifts as he usually did, telling his family he had “work to do tonight.” He then texted his boss to say he was not coming to work.

Less than a half-hour before the attack, he went to a convenience store. When the clerk said he would see Adan later, Adan replied: “You won’t be seeing me again,” Thornton said.

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.