yes it is true that the hanging man in the first room will fall if shoot enough times i found the ray gun was the easiest to make it fall make it fall and only takes about a clip and a half to do it now it wont crash the game if it falls but when you walk on it a crouch it will down you (like in campaign) and restart the game at round 1 but you will still have the same downs as before and the man will still be on the floor except nothing will happen if you go near it
NOTE- if the man falls and a zombie walks over it they will die but only works before the game crashes

Hope this was of some help to everyone