In October 2011, the police-related shooting death of unarmed man, Michael Nida, 31, raised serious questions about the state of policing in the city of Downey, California, a suburb of Los Angeles.

Why did it raise questions? The father of four who worked in construction wasn't shot with a handgun by one of the Downey Police Department's officers. He was shot with an MP5 submachine gun, the same gun used by the Navy Seals.

"Why would he have a machine gun?" asks Jean Thaxton, one of Nida's guardians since birth. "We're not in a war zone, I didn't think. I didn't think this was a war zone."

"An ordinary patrolman isn't going to be carrying something like a submachine gun," says Timothy Lynch, the director of the Project on Criminal Justice at the CATO Institute. Lynch says that even if they have those types of weapons, they should only be using them in rare circumstances, such as when they are confronting a heavily armed suspect.

But for decades police have been arming themselves with military equipment like M16s, grenade launchers, and armored personnel carriers.

"At first when they got it, the idea was, yeah, this is extraordinary weaponry, we'll have it just in case we'll ever need it." But as decades went by, police started to use them to enforce drug warrants and then started carrying them on routine calls.

Approximately 7:30.

Written and produced by Paul Detrick. Camera by Jim Epstein, Joshua Swain and Tracy Oppenheimer.