The officer tried to conduct a "routine" traffic stop following an unspecified violation by a driver around 7:30 p.m. Saturday. The driver, though, continued driving and hit at least two other cars, Chamberlain said.

The suspect then got out of his car and walked toward the officer, Chamberlain said, and "appeared" to be walking toward a handgun that was at the scene. Chamberlain said the suspect continued to walk toward the officer "in an aggressive posture" and appeared to shout for other people at the scene to confront the officer with him.

The officer, whom Chamberlain said was working alone and had backed into the intersection during the exchange, eventually fired "one to three rounds" at the suspect. A witness who told Denver7 they were in the first vehicle that was rear-ended by the suspect vehicle said "at least three" shots were fired.

Firefighters who arrived at the scene thereafter pronounced the suspect dead.

Much was unknown about the specific details of the exchange between the officer and the suspect prior to the shooting, Chamberlain said. A witness said at one point the suspect was walking away from the officer, but that the two "engaged" for about a minute-and-a-half to two minutes before shots were fired.

It was not clear where the handgun at the scene came from. A witness who spoke to Denver7 said the suspect was unarmed and that no weapon was visible. An investigation will also examine the aid – or lack thereof – provided to the suspect by the officer. A witness stated that multiple officers on the scene did not render aid.

"It doesn't appear that [aid] was allowed for based upon the actions of the individuals around and even based upon the actions of the suspect," he said.

Chamberlain said, though, that body-worn cameras, Flock cameras in the area, and potential bystander video all may have captured the incident on video.

He promised a thorough investigation, which would happen in conjunction with the district attorney's office.

"We are going to do everything, both internal and external, to make sure that this investigation is transparent, it is 100% valid, and it is factual," Chamberlain said. "This isn't something that we are going to have answers to overnight. But I also want [people to know] without any question, that we will give 100% of the facts – good, bad or indifferent – about what happened here tonight, and that is what I want to let people know."