If someone with a gun didn't know his gun kills people is this a defense?

A guy liked a lot of gun movies and thought guns don't kill people really it's all just movies like Beverly Hills Cop, James Bond, Harrison Ford movies,

So he took an M60 machine gun and starter shooting/killing like a whole bunch of innocent random people and then was saying "I'm James Bond"

Then he was surrounded by a SWAT team and forced to surrender his gun and in his defense he says "I honestly didn't know my gun was Really killing real people I thought they were faking dead to play James Bond with me I didn't know"

When he found out he shot/killed 58 people never going back, he fainted and cried for days

Will he be able to get off?

It would take a deranged person to honestly believe that. They call that incompetence to stand trial.

That would be called not guilty by mental defect. The person would be institutionalized in a mental institution for the criminally insane.

Go for the obvious on this one.

Then he would be recognised as a psychopathic teenager who had prepared his defence in advance

Where would a civilian who doesn't know guns kill people get access to an M60? Those may available to the public if you have a federal license, but even then those are fairly rare.

Sounds like a load of BS, or a liberal anti-gun fantasy, to me.

No