When Elaine takes Winston's shotgun and unloads it, she unloads the second shell twice, appearing to unload three shells from a two shell weapon.
When Patrick is examining the body at the start, he declares "the blow to the head" to be the killing blow. What he wants to say is that it is the "coup de grâce" - in archaic French, the "merciful blow", the final stroke to dispatch someone in pain (frequently a disabled opponent or colleague). What he actually says is that it is the "coup de gras", which sort of translates as "fat cut".