This undated photo released by the Douglas County Sheriff's Office shows Matthew Riehl. The 37-year-old man was shot to death Sunday, Dec. 31, 2017, after shooting at the deputies, killing one. Authorities in suburban Denver are investigating what led Riehl to fire more than 100 rounds in his apartment on sheriff's deputies. (Douglas County Sheriff via AP)

HIGHLANDS RANCH | Douglas County authorities say police were justified in shooting a gunman after he killed a Highlands Ranch deputy and wounded four other officers late last year.

Deputy District Attorney Jason Siers says Matthew Riehl posed a “deadly threat” to officers who responded to the shooting.

According to police, Riehl called 911 twice early on Dec. 31. When deputies on the second call came into the apartment to take Riehl into custody on a mental health hold, he opened fire from behind a bedroom door.

In a letter released Monday, Siers wrote that Riehl continued to shoot at SWAT team members who came to retrieve the slain deputy. He found the officers who fatally shot Riehl were defending themselves and others.

The letter says Riehl also wounded two neighbors as he exchanged gunfire with police.

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