THORNTON, COLORADO (REUTERS) - Police in Colorado on Thursday (Nov 2) captured a man who they had said calmly walked into a suburban Denver Walmart and fatally shot three people before driving away.

The Thornton Police Department said on Twitter that Scott Ostrem, 47, had been taken into custody. It did not immediately give details.

The authorities had released a surveillance camera photograph of a middle-aged white man wearing a black jacket and blue jeans. They also published a photo of the red four-door hatchback he is believed to have fled in.

Ostrem "nonchalantly" entered the store in Thornton, about 10 miles (16 km) northeast of downtown Denver, and opened fire on shoppers and employees a little after 6 p.m. time, Thornton Police Department spokesman Victor Avila told reporters, citing witness accounts.

"What we have determined is that it is random as of right now," Avila said. "As witnesses stated, the person came in and just shot towards a group."

Two men were killed in the shooting and a woman who was shot was taken to a hospital where she died, according to the police department.

Avila told Reuters that Ostrem was a "local" but said he could not give more details while the investigation is under way.

Police had initially said "multiple parties" were injured in the shooting and told the public to avoid the area. The Walmart was quickly surrounded by police and fire crews. About an hour after the initial alert, authorities said the threat of gunfire had ended.

Avila said there was no indication the shooting was an act of terrorism as no one has claimed responsibility. "We can't rule anything out," he said.

Thornton is city of about 120,000 people roughly 16km northeast of downtown Denver.

A Walmart customer, Aaron Stephens, 44, of Thornton, told Reuters he was inside paying for groceries at a self-checkout stand when he heard gunshots and the sound of ricocheting bullets.

"The employees started screaming and the customers started screaming" as people began to flee the store, he recounted. "I ran out, too, because I didn't want to get shot." Stephens said he did not see where the shooting had come from and did not see anyone struck by bullets.
Local NBC television affiliate 9NEWS reported that a woman whose son was in the Walmart had told her that he had heard about 30 gunshots and was still inside.

A video posted on Twitter showed the Walmart, which is in a large complex of big-box stores and other retail outlets adjacent to U.S. Interstate 25, apparently empty except for police officers with guns drawn.