I don't know much about guns, but taking it for granted that both, all , these policemen were shot with Dez's home made weapon.. ( he took the police Smith and Wessons on his way out ) could he make one that fires quickly? that quickly? that the second police had no time to duck, and/ or would that have to be a case of Dez having 2 guns, both loaded, one on him for the doorway and one propped up, loaded and unlocked ready to fire from the window?
I am just trying to work out the mechanics of it. Plus, of course, the third shot, we assume only 3 shots but we don't know that for sure. Or, a second shooter?