Some bull types will just bite harder the more you thrash them. doesn't matter how sturdy the stick or whatever. A good knowledge of how to break a bull breed off, helps a whole lot. Sad i know but the amount of bull types floating about now means at some time or other you are going to come into some sort of contact. A second or 2 is all it should really take and thus saves one hell of a vet bill.
Edited to add...i hope your Mother is ok mate and not too distressed about the whole thing and hope the tyke makes a speedy recovery