Caution tape marks the parking lot outside a King Soopers grocery store where a mass shooting took place a day earlier in Boulder, Colo., Tuesday, March 23, 2021. Credit: David Zalubowski / AP

BOULDER, Colo. — The suspect in the Boulder supermarket shootings bought the assault rifle six days before the shooting where 10 people were killed, including a police officer, according to an arrest affidavit released Tuesday. The documents did not detail where the gun was purchased.

The affidavit also said employees of the supermarket told investigators that the suspect identified by police as Ahmad Al Aliwi Alissa, 21, shot an elderly man multiple times outside the store before going inside.

Another person was found shot and in a vehicle next to a car registered to the suspect’s brother, the affidavit said.

Multiple 911 calls paint a picture of a chaotic, terrifying scene, according to the affidavit.

One said the suspect had opened fire out the window of his vehicle. Others called to say they were hiding inside the grocery store as the suspect opened fire on customers.

There were reports of “parties down” and that a male suspect had shot at police. Witnesses called to describe the shooter as having a black AR-15 style gun and blue jeans and reported he might be wearing body armor.

By the time he was in custody, Alissa had been struck by a bullet that passed through his leg, the affidavit said.

He had removed all of his clothing and was dressed only in shorts. Blood ran down his leg and 10 people were dead, including a police officer shot to death at the scene, police said.

Patty Nieberg and Thomas Peipert, The Associated Press