Just to clear up the argument (also post on here, not on the other thread that isn't meant for it):

If someone pulls a gun whilst you're next to them obviously it wouldn't be RDM if you kill them. It's a threat, especially if their job does have potential of hurting you (for example, if it's another cop that pulls their gun rather than a gangster it would count as RDM).

Obviously this is a threatening situation and this should not be counted as RDM.