It is difficult to completely understand the context of what happened here, the clip being deleted is suspicious but doesn't prove any mal-intent. It would appear from what you said and what jacob said that this wouldn't be RDM under killing rule #5, as if an attempted mugging took place, and they walked back a few minutes later and got shot, it is quite reasonable that someone would be shot.
You may kill in self defence or in defence of your partners/faction/property. When you've been attacked by an aggressor and survive (you did not aggravate or bait them to hit you) you may return with a weapon to kill them
-If someone has committed an offense against you (Act of violence, mugging, etc) you may recognize them based on their voice, character descriptions and clothing for up to 30 minutes afterwards (Without having their F3). Players may change clothes or lay low during this time to avoid recognition.