SWAT team

Four officers, including Parrish, were shot from a bedroom around 6 am, forcing the retreat. A SWAT team entered the apartment at about 7:30 am in an exchange of gunfire that left the gunman dead and another officer injured.

The suspect was well-known to authorities in the Denver area but had no criminal record, said Spurlock, who declined to name the shooter until his identity was confirmed.

Governor John Hickenlooper ordered flags on all public buildings immediately lowered to half-staff until Tuesday evening in Parrish's honor.

US 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!"

It occurred on the final day of a year that saw the deadliest mass shooting in modern US history in Las Vegas.

Ap - Reuters