Hypothetical/Real world question

[United States]Recently there have been videos circulating the web of a group of brothers who are actors that wear "traditional Arab garb" and drop backpacks near bus stops and other unsuspecting people's, then run away causing terror. They film these reactions and post them.

A rumor, most likely phony, surfaced the other day that one of the brothers was shot doing one of these hoaxes. Snopes has said that this is untrue.

My question is if someone were to actually shoot someone under the impression that someone just placed a bomb next to them, what would the legal repercussions be? Let's say, for the sake of clarity, that the person is mortally wounded.

Could it be considered self defense? I know that a reasonable belief of fear is given but does that allow force, specifically force to be used??

Any help would be great