A bystander and the suspect were also killed, officials said.
Arvada Deputy Chief Ed Brady said the bystander and suspect’s identities will be released by the coroner’s office once they are available. The officer’s identity is being withheld pending the notification of next of kin.
The city of Arvada is located about 10 miles north of Denver.
The incident began around 1:15 p.m. when an officer responded to reports of a “suspicious incident” in the Old Town Square, Brady said. Just after 1:30 p.m., 911 calls came in about shots fired, and that an Arvada police officer had been hit by gunfire.
“We heard at least four gunshots and we ran inside of the restaurant and people were diving under the tables and then the managers tried to get everyone down to the basement,” Michelle Engelbrecht, who witnessed the shooting, told CNN on Monday.
Veronica Carlson, the manager of Hunter Bay Coffee, told CNN she was in the basement of the shop when an employee ran downstairs. The employee had been on break outside when gunshots were heard, Carlson said.
“We ushered everyone away from the windows (and) tried to keep them happy and give them drinks if they wanted to,” Carlson said.
Brady said there were many “moving pieces” in the investigation but that there was no threat to the community. No other suspects are being sought, he said.
The officer was only the third to die in the line of duty in Arvada Police Department history and the first to die in a shooting, Brady said.