2nd Admendment, Gives You the Right to Bear your Ass

I am not a lawyer and cannot comprehend the fine tuning of small print of complicated double-negative words and all.  I was under the impression that the 2nd Admendment gave people the right of to bear ams for a millitia.  Now, not only do they have the right to use them in a militia, which they never do, but it also gives them the right to go on wild shooting sprees in public schools, theaters, and other places whenever they want.  Of course, if they do kill people they will be punished unless, somehow they get a smart lawyer who can show that all those school kids or all those people in the theater was a threat to him, then the killer can claim self defense under the "Stand Your Own Ground Law".