I am not gonna cap anyone!!
What is the meaning of Cap?No guys, i don't think, okay i gotta tell you the whole context, it was just a principal of a school arguing with a young pupil who's got a lot of troubles with the other pupils, and while they were arguing together the pupil exactly said the following: Okay, I am not gonna cap any motherfuckers........Sorry that what he said; )...please answer urgently
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Question

I am not gonna cap anyone!!
What is the meaning of Cap?No guys, i don't think, okay i gotta tell you the whole context, it was just a principal of a school arguing with a young pupil who's got a lot of troubles with the other pupils, and while they were arguing together the pupil exactly said the following: Okay, I am not gonna cap any motherfuckers........Sorry that what he said; )...please answer urgently
Thanks

Answer

I'm not gonna cap anyone can also means I'm not going to shoot anyone.  Obviously, if the context you heard this in was in a business boardroom or with respect to a sport player's salary, then yes, it would mean to set a limit.  If you heard this in an action movie, then it would probably mean to shoot.

Answer

Your sentence would refer to setting a limit, a budget, cost or ceiling on a person's salary.