A jury found Jeremy Webster guilty of killing a 13-year-old boy and wounding three others in a road-rage shooting spree in Westminster five years ago, rejecting Webster’s claim that he was insane during the attack.

The jurors convicted 28-year-old Webster on all counts, including one count of first-degree murder, six counts of attempted murder, four counts of assault and a single count of attempted assault.

Immediately after the verdict, District Court Judge Priscilla Loew sentenced Webster to life in prison without parole, plus 336 more years in prison.

“This case is really unlike any other case with the level of tragedy and loss,” she said.

Webster killed 13-year-old Vaughn Bigelow Jr. and shot the boy’s mother and brother during the June 14, 2018, attack in the parking lot of a dentist’s office at West 80th Avenue and Sheridan Boulevard. Webster pleaded not guilty by reason of insanity to the charges and claimed to have had an out-of-body experience during the killing.

Defense attorney Rachel Oliver told jurors during closing arguments Wednesday that Webster suffered from severe mental health problems for two decades before the attack, including hallucinations, suicidal and homicidal impulses, and breaks from reality. He did not remember the attack until police investigators began telling him details about what happened, at which point it came back to him in bits and pieces, “like a nightmare,” she said.

“He is not in his body,” she told the jury. “He is not even in his emotions. He is completely detached from himself, from this world, from everything around him. He has no present awareness of what is going on.”

Prosecutors said during closing statements that Webster’s long-term mental health struggles did not mean he was legally insane during the attack.

“Their own expert tells you that he was suffering from no psychotic episode,” Assistant District Attorney Jess Redman said. “While he talks about being the devil, he doesn’t believe he’s in some alternate universe. You heard (about) these disorganized thoughts, crazy notions of coins in fountains… that’s not June 14, 2018. June 14, 2018, is road rage.”

Webster followed Meghan Bigelow and her three children to the dentist’s office after becoming enraged when she merged in front of him on Sheridan Boulevard. After the two adults shouted at each other in the dentist parking lot, Webster pulled a handgun and shot Meghan Bigelow and two of her sons, 7-year-old Asa Bigelow and 13-year-old Vaughn Jr. Witnesses testified during the jury trial that Webster walked up to the cowering children, placed the gun against the back of their heads and shot them at point-blank range.

Webster also shot a bystander who witnessed the attack. Vaughn Jr. was killed; the other victims were seriously injured but survived.

Jurors deliberated for about three hours Wednesday after listening to evidence for two weeks in Adams County District Court. During sentencing, Meghan Bigelow spoke about the lasting trauma of the attack, and about missing Vaughn Jr.

“All his friends are graduating high school right now and going to college,” she said. “Every time I get one of those graduation cards, I burst into tears… We can’t hug him. We can’t laugh with him. We can’t joke.”

She added that Asa has endured more than 30 surgeries since he was shot.

Dentist Sean Whalen also spoke during sentencing, and said everyone involved in the attack was “forever changed.”

“I went from fixing a little girl’s tooth to running out in a parking lot where there were three bodies on the ground,” he said. “I’m shaking today — and it was five years ago.”

If Webster had been found not guilty by reason of insanity, he would have been committed to a mental health facility for treatment, rather than prison, and could have been released if he was later found to be sane. He did not speak during sentencing; his attorney said he planned to appeal the verdict.

Oliver told jurors that Webster’s mental health problems began when he was 4 years old and got worse as he grew into adulthood. He experienced hallucinations, and in the months before the killing, Webster believed his dog was the reincarnation of the ancient Egyptian queen Cleopatra, thought that a nuclear explosion had happened in Colorado Springs and that he was living in an alternate universe, and twice attempted suicide, Oliver said during closing arguments.

Webster heavily used alcohol and marijuana as a way to self-medicate, she said. But in early 2018, Webster started attending Alcoholics Anonymous meetings and achieved sobriety — aside from a one-day relapse in February 2018, she said. He then sought out mental health care and began taking several new medications.

“It’s scary to think that as we walk in the community there are people walking right by us who are struggling to the level that Jeremy Webster was struggling, but it is accurate, it is truthful,” she said. “He was struggling.”

Prosecutors in their closing arguments focused on Webster’s actions during the attack and said he knew what he was doing and was in control of his own actions, and that his claim of insanity was an excuse to try to avoid responsibility.

“He pulled the trigger until there were no more bullets,” Chief Deputy District Attorney Jennifer Prince said. “Intent. Deliberation.”

Loew said during sentencing that she did not consider Webster’s mental health struggles to be mitigating factors in his sentencing. She sentenced him to the maximum possible sentence on every count.

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Updated at 1:45 p.m. April 26, 2023: This story was updated to correct Asa Bigelow’s age during the attack.