The lone suspect was "shot & believed to be dead" after the standoff at the Copper Canyon apartment complex in Highlands Ranch, 20 kilometers south of Denver, the Douglas County sheriff's office tweeted.
Details of the incident were not immediately clear.
The wounded were taken to two area hospitals, at least three of them with noncritical injuries, the Denver Post reported.
Deputies had responded to an early-morning call of a disturbance when shots were fired from the building. Police quickly dispatched a heavily armed SWAT team as well as a bomb-squad truck, though there was no immediate word of any explosives being found.
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As the incident unfurled, the sheriff's office advised local residents to take cover in place and stay away from windows.
The toll among deputies today appeared to be one of the highest in a police-involved shooting since five officers in Dallas, Texas were shot to death and several others injured in July 2016 by a man angered by police shootings of black men.
The area near today's shooting has been scarred by dramatic mass shootings in recent years, including the Columbine school shooting in 1999, which left 15 people dead, and the 2012 shooting at a movie theater in Aurora that claimed 12 lives. Both are within a half-hour's drive of Highlands Park.