Police say the gunman who calmly walked into a suburban Denver Walmart and fatally shot three people has been captured. Scott Ostrem, 47, was taken into custody near his apartment. (Reuters)

A man suspected of calmly walking into a Colorado Walmart and fatally shooting three people was captured without incident Thursday morning, police said.

Scott Ostrem, 47, was picked up near his Denver home after police received a tip from a citizen. The capture ended a manhunt that began after police say Ostrem opened fire in the Thornton, Colo., store in suburban Denver, apparently at random, then turned around and walked out.

“From the witness accounts, he nonchalantly walked into the front of the business through the south door and just raised the firearm and began firing,” Thornton police spokesman Victor Avila told reporters at a news conference Wednesday night.

The Adams County Coroner’s office on Thursday identified the victims as Pamela Marques, 52, of Denver; Carlos Moreno, 66, of Thornton; and Victor Vasquez, 26, of Denver. Moreno and Vasquez died at the scene, while Marques succumbed to her injuries at the hospital.

Police and witnesses described a chaotic and confusing scene as the shooting started around 6 p.m. Wednesday. Hearing the gunshots, hundreds of customers tried to flee the store. Some customers pulled their own concealed weapons, Avila said. Unsure if the gunman was still inside, police cordoned off the area, blocking people from leaving the scene.

Once police determined that the shooter was gone, they enlisted the help of Walmart employees, who reviewed hours of surveillance video to identify a possible suspect.

The surveillance cameras captured a crisp image of the suspect — a slim man with a receding hairline, his hands jammed in the pockets of his black jacket. Police circulated the picture on social media late Wednesday, including images of what was believed to be his car, a red 2017 Mitsubishi Mirage.

Aaron Stephens was wrapping up a grocery shopping trip when he heard the distinctive pop of a gun, he recalled Thursday. Like those around him, he paused a beat and looked around. “After two more shots, I heard a woman scream bloody murder, like the worst bone-chilling scream you could hear,” he said. “Then, all the customers and staff started running around like crazy.”

Stephens, 44, a children’s book author, said he “hit the ground. Because I don’t know where the bullets are coming from. … I kept thinking, I don’t want to get shot. I don’t want to die.”

Jay Quawrn Thompson, an 18-year-old Walmart employee, was working in the back of the store when he heard the shots.

“A lady came running back, screaming about the shots,” Thompson told the Denver Post. “I got her out.”

The Walmart was still closed as of Thursday morning, Thornton Mayor Heidi Williams said.

In a statement, Walmart spokesman Ragan Dickens said the store’s employees are all accounted for and safe.

“We are relieved that an arrest has been made in this case,” he said. “Our thoughts and prayers continue to be with the families who lost loved ones and on supporting our associates. We will continue assisting law enforcement however we can.”

Police have not released a motive for the shooting.

Moreno was a well-known fixture at the Auraria Higher Education Campus, a large college in downtown Denver where he worked for 18 years. He worked as a structural tradesman, doing repairs of various kinds, spokesman Blaine Nickeson said.

“He had a lot of staff and faculty on campus that relied on him and felt like he was someone who gave them great customer service,” Nickeson said. “He was easy to engage with and always had a smile on his face.”

Vasquez was a father with two little girls and another child on the way, according to a GoFundMe site set up to raise money for his family.

According to public records, Ostrem worked in the construction industry, including as a sheet metal fabricator. Over the years, he started at least two businesses that are now delinquent, according to the Colorado Secretary of State. Ostrem frequently moved, most recently settling in a drab apartment building on Samuel Drive in Denver. In 2015, Ostrem filed for bankruptcy.

In 2013, Ostrem was arrested in nearby Wheat Ridge for driving under the influence of alcohol, according to police records. Court records also show that he was charged in 1999 with resisting arrest, a charge that was later dropped.