A 47-year-old man suspected of walking into a store and killing three people has been detained by police.

Colorado man Scott Ostrem was arrested on Thursday morning, about 14 hours after the shooting at a Walmart that witnesses said appeared to be random. His arrest followed a brief chase in which Mr Ostrem attempted to flee law enforcement, but was blocked by traffic.

Police had warned the Denver community that Mr Ostrem was “armed and dangerous”, and to avoid the suspect if he was seen in public. An anonymous tip later led police to the suspect’s home, which is about five miles away from the Walmart.

In interviews, police described a cool-headed shooter, who calmly walked into the supermarket before opening fire. After killing two men and a woman, the shooter simply left the building.

“He walked in very nonchalantly with his hands in the pockets, raised a weapon and began shooting. Then he turns around and walks out of the store,” Victor Avila, a Thornton police spokesman, said.

Mr Avila indicated that their description of the event was based on several witnesses in the Walmart, who said that the shooting appeared to be random.

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Aaron Stephens, 44, said he was in the self-checkout line in the supermarket when he heard a gun shot, followed soon after by more bursts of gunfire. The scene was pandemonium: customers were screaming and rushing as quickly as they could to the exits while the shooter casually left.

“I was scared,” Mr Stephens told The Denver Post. “I feared for my life.”

The shooting was met with hundreds of emergency responders, who circled the Walmart and the shopping centre it is located in.

The three victims have yet to be named by police, though police say they were the only three victims of the attack. The woman who was shot was rushed to the hospital, but was later pronounced dead.

Others were treated for anxiety-related conditions following the shooting.

The attack is just the latest incident of gun-related violence in the US, where the problem runs rampant. The country has some of the highest rates of gun violence, including mass shooting events that typically gain broader media attention.

Hundreds of mass shootings have already occurred in 2017 alone, according to the Gun Violence Archive, which counts mass shooting events based on the FBI’s definition – any event in which four or more people selected indiscriminately, not including the perpetrator, are killed.

The US has more mass shootings than any other country in the world, a reality punctuated by high-profile incidents, such as the attack in Las Vegas where 58 people were killed and 500 more were injured after a gunman opened fire on a country music festival. That shooting, the worst in United States history, was just over a month ago. The study indicating that the US has more mass shootings than any other country is more refined than the FBI definition, and does not include gang killings or killings that involve multiple family members.