BOULDER, Colo. (AP) — The suspect accused of opening fire inside a crowded Colorado supermarket was a 21-year-old man who purchased an assault weapon less than a week earlier.

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That was the word from authorities on Tuesday, a day after the attack that killed 10 people, including a police officer.

An affidavit says Ahmad Al Aliwi Alissa bought the weapon on March 16, just six days before the attack at a King Soopers store in Boulder.

It was not immediately known where the gun was purchased.

Alissa is from the Denver suburb of Arvada.

He was booked into jail on murder charges. Investigators have not established a motive.

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