MADISON, Wis. — Prosecutors will not charge a security guard who shot and killed a man suspected of robbing Madison area banks wearing a "Deadpool" Halloween mask.

The guard fatally shot 35-year-old Luis Narvaez as Narvaez tried to rob a Madison bank on March 1. Narvaez was unarmed and was shot in the back from about 10 feet away.

Assistant Dane County DA Matthew Moeser says the guard, identified only by the initials "CD," thought Narvaez had a weapon because he kept his hands hidden in his pocket, and was worried Narvaez might try to take a hostage.

The Wisconsin State Journal reports Narvaez was linked to six other bank robberies in which the robber wore a "Deadpool" mask based on the superhero. Narvaez didn't wear the mask in the March 1 robbery.