Four people, including an armed suspect, have died during an hours-long police standoff at a Colorado townhouse, authorities say.
The shootings occurred on Saturday about 6.4 kilometres southeast of the Aurora Mall, where 12 people were killed and dozens wounded by a gunman at a midnight showing of the Batman film, The Dark Knight Rises, on July 20.
The man charged in that shooting, James Holmes, goes to court on Monday for a preliminary hearing in which prosecutors will lay out their case against him.
An Aurora police department special weapons team responded after shots were heard at the townhouse at 3am local time, said Aurora police Sgt Cassidee Carlson. Investigators said three people, all adults, appeared to have been killed before officers arrived.
The suspect shot at police at 8.15am and was killed during a shootout when officers stormed the home about 45 minutes later, Carlson said. It wasn't known if officers shot the suspect or if he shot himself.
A fifth person escaped unharmed before officers arrived and reported that she saw three people inside the home who 'appeared lifeless', Carlson said.
The sergeant declined to elaborate about the woman's escape.
A motive for the killings was unknown. Police were going over the crime scene.
'We're just getting in there with our crime scene detectives, so obviously we'll have to determine if it was our rounds or his rounds,' Carlson said.
Police declined to release the name of the suspect or victims.
Officers evacuated neighbours during the standoff and used a bullhorn to communicate with the gunman, urging him to surrender.
Aurora, just east of Denver, is one of Colorado's largest and most diverse cities with more than 335,000 residents. It is home to Buckley Air Force Base as well as the sprawling University of Colorado Health Sciences Center campus.