The suspected shooter in Monday’s attack at a Boulder supermarket that left 10 people dead purchased his firearm at a local gun store after passing a background check, according to authorities and the shop owner. 

The Associated Press reported that 21-year-old Ahmad Al Aliwi Alissa also allegedly had a second weapon with him on the day of the attack, a 9 mm handgun in addition to the AR-15 assault rifle that police recovered. 

According to the AP, the suspect did not use the handgun during the attack, instead firing shots with the rifle that police say was purchased just six days before the shooting. 

John Mark Eagleton, owner of Eagles Nest Armory in the Denver suburb of Arvada, told the AP that the suspect passed a background check by the Colorado Bureau of Investigation before purchasing the gun from his store. 

“Our hearts are broken for the victims and families that are left behind,” Eagleton said. “Ensuring every sale that occurs at our shop is lawful, has always been and will always remain the highest priority for our business.” 

Boulder Police Chief Maris Herold said at a news conference Friday that investigators were still looking for a motive for the attack, including why the suspect chose that particular store and what fueled him to carry out the shooting. 

“Like the rest of the community, we too want to know why — why that King Soopers, why Boulder, why Monday,” Herold said, according to the AP. “Unfortunately, at this time, we still don’t have those answers.”

Boulder County District Attorney Michael Dougherty said they have a suspected number of how many shots were fired in the gun battle between police officers and the alleged shooter Monday, though he added they were not ready to reveal this to the public yet. 

Officer Eric Talley, who was the first to respond to the shooting, was one of the 10 people killed. 

Dougherty said the response by police “saved other civilians from being killed.” 

Alissa, who appeared in court Thursday morning, faces 10 counts of first-degree murder and one count of attempted murder. He is currently being held without bail. 

The shooting has brought up renewed debates among elected officials on the need for gun control legislation, with Democrats calling for more stringent background checks for gun purchases as well as reimplementing a federal assault weapons ban.