Police arrest 'gunman', 47, who 'shot and killed three shoppers after he "nonchalantly" walked into a Denver Walmart and started firing at random'rt-leaves-multiple-injured.

Police have arrested the suspect who allegedly opened fire at random inside of a Denver-area Walmart on Wednesday night and killed three people.

Scott Ostrem, 47, was captured and taken into custody 10 hours after he 'nonchalantly' walked into the store in Thornton, Colorado, on Wednesday night and started firing at shoppers near the cash registers, according to cops.

Video captured at 8am on Thursday morning shows him being led into a police SUV wearing handcuffs.

The three victims, two men and a woman, were all in the same area near the front of the store at the time of the shooting, Thornton police spokesman Victor Avila said.

The gunman did not say anything during the shooting and walked back out and fled the scene in a red, four-door Mitsubishi Mirage.

Police do not believe the shooting is related to terrorism, but they have not ruled anything out. A motive is not known and little information about Ostrem has been released.