Four people were fatally shot and a police officer and two other people were injured on Monday night in the Denver area by what appeared to be a lone gunman, who was later killed after a shoot-out, the police said.
The killings unfolded across several locations in and around Colorado's capital and the authorities said the suspect's motive was not immediately clear.
Denver police chief Paul Pazen told reporters during a news conference: "This is the holiday season. To have this type of spree take place is not normal for our community."
The shootings started after 5pm in central Denver, where two women were killed and a man was injured, he said.
Another man was fatally shot several blocks away, the chief said, and police officers exchanged gunfire with a suspect during a pursuit.
After disabling a police car, the same suspect fled south-west to the nearby city of Lakewood, he added.
Just before 6pm, the Lakewood Police Department received a report of shots fired at a business, Mr John Romero, a spokesman for that department, told reporters during a joint news conference with Mr Pazen.
A gunshot victim was later found and pronounced dead at the scene, Mr Romero said, adding that police officers identified the car and the shooting suspect. But they did not publicly reveal his name.
When the officers found the car, the gunman opened fire and officers shot back, Mr Romero added.
He then fled on foot to a Hyatt Hotel, where he is believed to have shot a clerk. He also shot and wounded a police officer after he left the hotel.
The hotel clerk's condition was not immediately clear as at Monday night, and the wounded officer was undergoing surgery, Mr Romero said at the news conference.
Mr Paul Osckel, a spokesman for the Lakewood Police Department, said that he had no further information on the officer's condition.
Mr Romero said the suspect was later shot in Lakewood and pronounced dead at the scene. It was not immediately clear if police officers had shot him.
Mr Pazen said that, based on preliminary information, the Denver Police Department believed that the same person was responsible for the shootings and the earlier shoot-out with the police.
A number of mass shootings have taken place in Colorado since two students at Columbine High School shocked the nation in 1999 by killing a teacher and 12 classmates.
In March, a gunman killed 10 people at a Boulder grocery store, including a police officer.
