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 on Thursday.

'We were told (he) had not previously shown an interest in religion,' FBI Special Agent Rick Thornton said at a news conference.

He said 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.

'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.

During the news briefing, authorities released graphic videos of the September 17 attack, showing parts of Adan's rampage through the Crossroads Center mall, and his fatal confrontation with off-duty Avon Police Officer Jason Falconer.

All 10 people who were stabbed during the attack survived their injuries.

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During a news conference on Thursday, authorities released mall surveillance video showing 20-year-old Dahir Ahmed Adan attacking victims (pictured) and the moment he was shot

Adan (pictured) 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 on Thursday

The attorney for Adan's family, Abdulwahid Osman, said Adan's 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.'

Hours before the attack, Thorton said Adan had stopped at Super America, a convenience store that he often visited in St Cloud, The Star Tribune reported.

As he left the store he told the people inside, 'You won't be seeing me again,' according to Thorton.

On his way to the mall, he struck a bicyclist who rolled across his hood and cracked the windshield of his Camry.

He kept driving and went on to run a red light before arriving at the mall's south parking lot.

During the attack, which started outside the mall before moving inside, witnesses told the FBI that Adan, who was armed with two steak knives and later shot and killed, referenced Islam.

In one video, Adan entered Unique Electronics and attacked an employee, swingingly wildly with a knife. The clerk is stabbed in the back before the victim fleed to safety

Adan then ran through the mall stabbing victims in the head, chest and neck as shoppers frantically ran for cover.

'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.

In one video, Adan is seen swinging wildly at an electronics store clerk and stabbing him at least once before the man scrambled away.

Before Adan entered the store, the Unique Electronics employee was sitting behind the counter before running to the entrance to see the commotion in the mall.

Shoppers are seen running past the store before Adan runs past and then approaches the employee.

Narrating the video, St Cloud Police Chief Blair Anderson said Adan asked the clerk if they were Muslim but the victim does not respond and the attack begins with Adan stabbing the individual.

In a second video, frightened shoppers inside Northwoods Candy Emporium are seen running out the store as Adan approaches

A quick-thinking employee is able to pull down the metal gate to the store

Adan is pictured above trying to enter the store after the employee pulled down the metal gate. He runs off and continues his gruesome attack

The terrified employee is seen trying to get out of harm's way but falls over.

Adan then stabs the victim in the back, causing his knife to bend, before pulling out a second knife.

The employee moments later is seen running out of the store to safety.

TIMELINE OF EVENTS LEADING TO THE SEPTEMBER 17 STABBING ATTACKS 3pm: Adan returns home from a shift at work, but does not change from his uniform or take a nap, as was his usual custom. When asked why, he responded by saying he 'had work to do that night.' 7.54pm: He stops at Super America, a convenience store he frequented. When leaving, a clerk said 'See you later,' and Adan responds, 'You won't be seeing me again.' 8.02pm: He returns to his apartment briefly before leaving for Crossroads Mall five minutes later. 8.09pm: He hits a bicyclist on the way to the mall in a hit-and-run accident who cracks the windshield on his Camry. 8.13pm: He arrives at the mall and begins his rampage outside just one minute later. Source: KARE11 Advertisement

Officials noted they initially were not aware of the victim in the electronics store until canvassing stores at the mall asking if they had video of the attack.

A second video taken from inside Northwoods Candy Emporium shows customers running out of the store as Adan approaches.

The quick-thinking employee inside is able to pull down the metal gate to the store only moments before Adan tries to enter.

Adan stands at the gate briefly before running off to continue his gruesome attack.

In a third video, a bloody Adan is shown crawling and trying to get up after he was shot six times by Falconer inside a Macy's, who Stearns County Attorney Janelle Kendall said will not be charged.

Adan had approached Falconer asking if he was Muslim to which the officer says no before telling Adan he was a cop and to put his knives down, Kendall said.

The attacker charges at the officer before Falconer shoots him.

Adan attempts to crawl toward Falconer with a knife in his hand, despite being shot.

He attempts to get up several more times and is shot a total of 10 times with six bullets striking him, Kendall said.

Kendall announced during the conference that she found Falconer, who has been hailed a hero, was justified in shooting the assailant, calling his actions 'justified and lawful.'

In video taken inside Macy's, it shows Adan's encounter with off-duty Avon Police Officer Jason Falconer shown here with his gun drawn

Adan is shown here lying still after being shot by Falconer but moments later is seen trying to get up

Adan, despite being shot several times, attempts to get up on all fours and crawls out of view. He was shot six times

'You're looking at an authorized use of deadly force,' Kendall said.

'He was faced with an individual in a busy mall armed with two knives, one in each hand, brought to his attention after he was asked if he was Muslim with people running and screaming in fear.'

Before his confrontation with Adan, Kendall said Falconer had been shopping at the mall for a gift for his daughter at Bath and Body Works.

She also noted that during Adan and Falconer's confrontation, Falconer showed his badge to frightened shoppers who were confused why a man in plainclothes was shooting a man in a security uniform.

Law enforcement also shared the mall surveillance video evidence with the family on Thursday, Osman said.

Scenes from outside the Crossroads Center mall during the September 17 stabbing attack

Scenes from outside the mall last month. When the brutal 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

'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.

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 had 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.

St Cloud Police Chief Blair Anderson talks about evidence photos of the knives used during stabbings at Crossroads Center during the press conference

Stearns County Attorney Janelle Kendall talks about video surveillance footage from the stabbing

It was not immediately known whether the extremist group had planned the attack or knew about it beforehand.

He said investigators are still working on Adan's digital footprint, including social media accounts, and have yet unlocked his iPhone.

He said investigators are assessing 'legal and technical options' for the phone.

Officials said Officer Falconer (pictured) was justified in his shooting of the assailant

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.'

Thornton did not elaborate on the FBI's efforts to get into Adan's iPhone, and agency spokesman Kyle Loven said he could not 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.

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.

St. Cloud Mayor Dave Kleis speaks during the conference. Kleis asked that people continue to think about those who were injured in last month's stabbing, as well as those who saw the attack