A gunman killed three people before police shot him dead this weekend in a shooting at a house in the Colorado town of Aurora, scene of a massacre at a cinema last year, police said.
A statement from the Aurora police department said a woman had escaped from the home and raised the alarm. When officers arrived, the man had barricaded himself inside with the corpses of his three victims.
"The male was given multiple commands to come out of the house both on the phone and from a bullhorn outside. He did not comply," the statement said.
"He was behaving very irrationally throughout the incident and often hanging up on the negotiators," it added, describing how a SWAT team of armed specialist officers had approached the building shielded by an armoured van.
"Upon doing so, the suspect fired multiple rounds striking the vehicle but not injuring any officers. Officers did not return fire. Over the next hour, gas was introduced and more commands were given to the suspect," it said.
"Shortly before 9:00 am, the suspect appeared in a second story window and engaged officers again with gunfire. Officers returned fire, striking the suspect," the statement added.
Entering the property, the team found the shooter dead, along with two other men and a woman. They have not identified the victims and an investigation has been launched.
Aurora made global headlines in July after a horrific shooting at a movie theatre that left 12 people dead and 58 others wounded during the first midnight screening of the latest Batman film, The Dark Knight Rises.
The Aurora cinema shooting revived America's perennial gun control debate, a dispute that only intensified last month when a gunman attacked a Connecticut elementary school, killing 20 young children and six staff members.