Joshua Cummings is being sought in the execution-style murder of RTD contract security officer Scott Van Lanken in Denver on Tuesday.

Joshua Cummings

Cummings walked up behind Lanken while he was talking to two women and shot him in the head.

Cummings posted several tweets critical of police before the shooting.

What makes you a cop? Not your badge, not your uniform, not your paycheck from the government, and it’s not your… https://t.co/BTfEBsiFm8 — Joshua Cummings (@Bjj_Joshua) November 13, 2015

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Police found jihadist materials in his backpack.

FOX 31 reported: