There's a voodoo shaman or something like that in our backyard?

My 13 year old little brother has been into some sort of voodoo or something (not sure what it is exactly he won't talk to us about it). I have been watching him and my 6 year old sister alone for the past couple of days. Last night he burned up my little sister's playhouse when he was doing some kind of ritual in there where he burned an effigy of Prophet Muhammad and left a bunch of blood vials, mirrors, etc, in it. Now he's in the backyard and there is some person standing with him dressed in a black cape and hood.