The Boulder police officer who shot the man suspected of killing 10 people in March at a King Soopers was legally justified, the Boulder County District Attorney’s Office announced Thursday.

Suspect Ahmad Alissa, 22, who currently faces more than 40 charges for murder and attempted murder for the March 22 massacre, received a gunshot wound to the thigh before surrendering. A decision letter from District Attorney Michael Dougherty confirms Officer Richard Steidell shot the suspect. Steidell will not face any criminal charges.

Dougherty’s decision letter sheds some additional light on how the law enforcement response to the shooting unfolded. According to the letter, the second wave of officers, including Steidell, entered the store at 2:38 p.m., and they were shot at within about 20 seconds.

Steidell initially returned fire with his handgun before dropping to the ground. The suspect went out of his line of sight for about 90 seconds, according to the letter, and fired a second round of shots when he could see the suspect again, who had once again aimed his gun at officers.

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The letter also says Steidell could see the suspect was armed with a long gun.

According to the letter, Steidell fired the last shots that afternoon. He estimated he fired one or two shots when he first returned fire at the suspect, and between five and 10 shots in his second round of fire, the letter says.

The investigation found he fired eight shots total, according to the letter.

Officer Eric Talley, who was among the first group of officers to enter the store, was killed in the massacre. According to the decision letter, Steidell came across the bodies of two other victims and Talley, but was not immediately certain whether Talley had been killed.

The investigation found Steidell was justified in not giving clear verbal warnings before shooting. According to the letter, verbal commands could have made it easier for the suspect to locate and fire at officers, placing them at “unnecessary” risk of serious injury or death. The letter also says other signals such as the officers’ uniforms, their marked police shield and clearly identifiable police vehicles outside announced the presence of officers.

“The shooter had already ambushed officers twice – once when he shot Officer Talley and again when he fired at the second entry team,” says the letter. “As Officer Steidell had determined, giving verbal warnings and waiting for the shooter to answer the warnings would have enhanced the shooter’s ability to locate and fire on the officers.”

In a news release, Dougherty thanked the critical incident team for thoroughly investigating Steidell’s shooting.

“This investigation has certainly highlighted the bravery Officer Steidell and his fellow officers who took such courageous action by charging into an incredibly dangerous and deadly situation,” he said.