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DENVER — A Denver jury found Joshua Cummings guilty of first-degree murder in the killing of RTD security officer Scott Von Lanken last year, the Denver District Attorney’s Office said.

He was sentenced to mandatory life in prison without the possibility of parole.

Police said two women were asking the armed security officer about light rail routes near 16th and Wynkoop streets on Jan. 31, 2017 when a man approached from behind, pointed a gun at the officer’s neck and fired.

Cummings was found hiding in the 1600 block of 14th Street about 20 minutes later and was arrested without incident, police said. A gun was also recovered.

During the trial, the defense said the shooting was neither deliberate nor intentional.

Prosecutors maintained Cummings thought he was killing a police officer when he allegedly walked up behind Von Lanken and shot him in the head.

The shooting was captured on a city halo camera and police said Cummings was arrested with the murder weapon containing both his and the victim’s DNA.

Two sources said investigators found jihadist materials in Cummings’ backpack and those materials were being investigated.

Cummings told The Associated Press he pledged allegiance to the Islamic State to purge the oath he took to uphold the U.S. Constitution when he joined the Army.