Chilling Video Shows Minnesota Mall Stabbing Suspect Attack Clerk

— -- Authorities in Minnesota released chilling surveillance video today showing suspected terrorist Dahir Adan attacking a store clerk at a Minnesota mall.

In the video, a man identified by authorities as Adan runs into a store and then attacks the clerk, who is the only other person seen in the store on the video. The clerk manages to escape the attacker's grasp and run from the store.

Adan, 20, stabbed multiple people at the Crossroads Center mall on Sept. 17 before he was fatally shot by off-duty police officer Jason Falconer, authorities said. Ten were wounded; no one had life-threatening injuries.

At a news conference today, authorities said collected evidence suggests that the attack was premeditated and that Adan had been radicalized.

Adan was armed with two steak knives when he approached and stabbed 10 people after first asking "some of them" if they were Muslim, authorities said. Others he stabbed, they said, without asking.

Falconer was shopping and legally armed when he saw Adan coming towards him, officials said. Adan asked Falconer if he was Muslim, and Falconer answered "no," he told authorities. Adan then turned away and Falconer saw two knives in Adan's hands. Falconer yelled that he was a police officer and ordered him to drop the weapons. Adan ran toward Macy's and Falconer followed, authorities said.

Surveillance videos from inside Macy's, viewed by ABC News, show Adan running into the store with Falconer following with his gun drawn. According to witnesses, Falconer was yelling that he's an off-duty officer and that Adan should drop his weapons. In the videos viewed by ABC News, Adan went towards Falconer. Adan was shot by Falconer several times during their encounter, according to authorities and the videos.

An official with the FBI's Minneapolis field office said that the investigation shows that, in the last few months, Adan had become interested in Islam and encouraged female relatives to become more observant. He became less interested in past hobbies, and went from being an excellent student to "flunking out of college almost overnight."

Authorities said they came across numerous accounts that day of Adan yelling "Allahu akbar" -- that is, God is great -- and "Islam, Islam" and asking people at the mall whether they are Muslim. Officials said the "totality" of his behavior suggests he may have been radicalized through others or on his own.

The local prosecutor said her office has reviewed all of the evidence, including video, and it was determined that Falconer "was justified in the use of deadly force," and no criminal charges will be filed again him.