A gunman, who was holed up in a house with several hostages, kept the police at bay for several hours, but the standoff ended with the killing of three hostages and the gunman.
Local media reports said that police broke into the house after hours of failed negotiations gunned down the culprit.
Three victims were discovered dead inside the home, Denver News reported.
Neighbours who heard gunshots from the house called the police at around 3 am (local time Saturday), following which police surrounded the house and evacuated the area.
According to a report in the local KUSA news, one person inside the home was able to escape the hostage situation and alert authorities.
The identities of the victims and the gunman were not released immediately.
Last year in July, the Colorado city of Aurora witnessed a macabre shooting incident at a movie theater screening The Dark Knight Rises, in which 12 people were killed and 58 were injured.
The US was shaken last month when a gunman barged into an elementary school and shot dead 20 little children and six school staffers, in one of a series of such shooting incidents that has sparked a gun control debate in the country.