Douglas County Sheriff Tony Spurlock said deputies came under fire almost immediately after entering a suburban Denver apartment and trying to talk with the suspect, who was holed up inside a bedroom.
"I do know that all of them were shot very, very quickly. They all went down almost within seconds of each other, so it was more of an ambush-type of attack on our officers," Spurlock said. "He knew we were coming and we obviously let him know that we were there."
The wounded deputies tried to pull the fallen officer, identified as Zackari Parrish, out of the line of further gunfire but were unable to because of their own injuries and only managed to "crawl to safety," Spurlock said.
The incident occurred around 5:15 a.m. at Copper Canyon Apartments, a landscaped apartment complex in Highland Ranch, 16 miles (28 kilometers) south of Denver. Authorities had left the home about four hours earlier to address a noise complaint but returned in response to reports of a disturbance at the home.
There were two men inside the home when deputies arrived and someone let them inside, Spurlock said. The disturbance was initially reported to be domestic but turned out to be noise-related, he said.
"The suspect was just making a ton of noise and annoying everyone around him," Spurlock said.
Vira Cover, who lives in a building about 50 yards away from the shooting, was woken up by a phone call from her fiance, Steve Silknitter, who warned her about what was happening and urged her to stay inside. Soon afterward she said she heard about 15 to 20 very loud shots fired over about 30 seconds or a minute. She sat on the couch with her cats and called Silknitter back before turning on the television to try to find out more about what was happening.
"I couldn't believe this was happening in our backyard," she said.
Silknitter heard the shots fired too but from about a half mile away, stopped at a police roadblock as he tried to get back home from work. Then he said he saw police in tactical gear speed past him in a pickup truck.
Silknitter said he lived 2 miles away from the movie theater in Aurora, Colorado where 12 people were killed in a shooting in 2012. He said he never would have expected anything like this in his apartment complex, where the only noise you might normally hear is children running around upstairs.
"Where do I move to where I don't have to worry about someone shooting us?" asked Silknitter, who is now considering getting a concealed weapons permit.
The suspect was well-known to authorities in the Denver area but had no criminal record, said Spurlock, who declined to name him until his identity was confirmed.
The sheriff did not release any details about the weapons and ammunition used except to say the suspect had a rifle. He also did not know if law enforcement had any prior knowledge of firearms being in the home but the possibility always weighs on deputies' minds.
"We respond to every call anticipating that everyone has a gun. This is Colorado. Everybody has a gun," Spurlock said.
Parrish, the slain officer, was 29 and a married father of two young children. He came to the department seven months ago after working as an officer for the nearby Castle Rock Police Department. Spurlock called him a "good kid" who was eager to work.
"His wife told me today that he loved this job more than he had loved any job he ever had," the sheriff said.
Gov. John Hickenlooper ordered flags on all public buildings immediately lowered to half-staff until Tuesday evening in Parrish's honor.
The three deputies and one police officer injured were listed in stable condition. Authorities identified them as deputies Michael Doyle, 28; Taylor Davis, 30; Jeffrey Pelle, 32; and Castle Rock police officer Tom O'Donnell, 41.
The two civilian injuries were not life-threatening.
Pelle is the son of Boulder County Sheriff Joe Pelle. The sheriff shared a picture of him and two other family members by his son's hospital bed on his office Twitter account. All four, including Jeffrey Pelle, who underwent surgery, are smiling and giving a thumbs-up gesture.
President Donald Trump expressed sorrow, writing on Twitter, "My deepest condolences to the victims of the terrible shooting in Douglas County @dcsheriff, and their families. We love our police and law enforcement - God Bless them all!"
The shooting occurred on the final day of a year that saw the deadliest mass shooting in modern U.S. history in Las Vegas.