At approximately 6:30 p.m. on Wednesday evening, a gunman opened fire at the Walmart Supercenter on Grant Street in Thornton, killing three people. The suspect, identified as 47-year-old Denver resident Scott Ostrem, was at large Wednesday night but was arrested and taken into custody Thursday morning, according to the Thornton Police Department.

Ostrem allegedly walked through the south entrance of the Walmart store with a handgun and began firing randomly, killing two men and one woman, according to Matt Barnes, a community relations officer at the Thornton Police Department. No others were injured by the shooter, Barnes says, but some people suffered injuries—some stemming from anxiety—during self-evacuation.

It’s still unclear how many shots were fired, as the Thornton Police Department continues to investigate the crime scene. After striking three victims, Ostrem allegedly walked out of the store casually, and drove away, Barnes says. He was arrested on the 7200 Block of Federal Blvd. in Westminster, not far from his residence.

According to Barnes, Ostrep was arrested “for investigation of three counts of first-degree murder,” and will face formal charges once he is taken to the Adams County detention facility. The shooting is being considered an isolated incident, but may ultimately be classified an act of terrorism

“We don’t see any nexus to any other events that have taken place locally or nationally,” Barnes says. “Anytime you have an incident like this with mass casualties you would possibly consider it domestic terrorism, but we’re not classifying it as terrorism at this time.”

While Ostrem does not have a substantial criminal history, he has had several run-ins with the police over the years and was described by his neighbors—who frequently saw him with a rifle case—as “creepy” and “evil,” according to reports from the Denver Post. He had also filed for bankruptcy after running two failed businesses and accrued nearly $60,000 in credit card debt.

The victims of last night’s shooting included Carlos Moreno, a 66-year-old Thornton resident and grandfather who was a structural trades technician at Auraria Higher Education Center, according to Fox 31 News. Victor Vasquez, a 26-year-old father of two girls, was also killed at the store. And Pamela Marques, a 52-year-old Denver resident, died after being transported to an area hospital.

Because at least three people were killed, last night’s shooting in Thornton is considered a “mass shooting,” one of more than 273 this year in the United States.

Jay Bouchard
Jay Bouchard
Jay Bouchard is a Denver-based writer and a former editor on 5280's digital team.