PHOENIX -- Police have arrested an Arizona man who allegedly filmed his 16-year-old nephew walking city streets dressed in a sheet and carrying a fake grenade launcher, authorities said on Wednesday.

The bizarre, amateurish video depicts a person with a fairly realistic but fake grenade launcher walking around a Phoenix intersection in what appears to be a blue sheet with dark material covering his head and face.

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Made eight days after the shooting at a screening of a Batman movie, the film was posted on YouTube and titled, "Dark Knight Shooting Response, Rocket Launcher Police Test."

"Given this event, I wanted to run a little test here in Phoenix, Arizona," the narrator says in the film. "I want to find out how safe I really am, and I want to know the response time of the Phoenix police department."

The filmmaker claims it took 15 minutes for police to respond.

The first officer finds the filmmaker and the teen standing in a driveway. The officer calmly tells the boy to put down the weapon and....MORE