BRIGHTON | A man charged with opening fire and killing three people at a crowded Walmart in suburban Denver pleaded guilty Wednesday to three counts of first-degree murder as part of a plea agreement that calls for him to be sentenced next week to life in prison without the possibility of parole.
Scott Ostrem, 48, also pleaded guilty to one count of attempted first-degree murder for the shots that endangered 30 other people in the store in Thornton. Sentencing is set for Oct. 19.
Police have said Ostrem walked into the store on a weekday evening, fired seven shots in about 20 seconds and left without saying a word.
Authorities have not discussed a motive for the Nov. 1, 2017, shooting.
Ostrem was working as a metal fabricator at a roofing company and his boss has previously said that Ostrem abruptly left work hours before the shooting. Police said they later learned that he went to a shooting range. Surveillance video showed Ostrem firing at a target for a few minutes, then leaving.
At a June court hearing, police said they had not found the murder weapon, but that shell casings found at the store matched those found at the shooting range.
Police used surveillance video from about 200 cameras inside and outside the store to identify Ostrem and his car in the hours after the shooting. He was arrested the following day after a brief car chase.
Ostrem’s stepsister, Michelle Willoughby, told The Denver Post that he has been tormented by voices in his head since taking LSD nearly 30 years ago.
She said Ostrem had been outgoing, sociable and athletic before taking the drug at a party, and afterward he became a recluse haunted by voices saying the devil was after him.
An Adams County judge ruled earlier this year that Ostrem was competent to stand trial based on an evaluation at the state mental health hospital.
Ostrem had been set for trial in January on six counts of first-degree murder and 30 counts of attempted first-degree murder.