In all cases, you may be sued civilly for a wrongful death, battery, or any number of other things. And lots of parties can bring the suit: the individual himself, various members of his family, your homeowners association, etc. N is fairly big, removing one of the N probably is not meaningful. Do these sort of civil suits tend to pay more for woundings than deaths? I have no data on this but would be surprised if that were the case.
I expect the only thing the OP meant is that slain person cannot testify the killer. This is self-evident but not really helpful. How is it different than "if you're going to rob someone, you should also kill them". I suppose this might be good practical, tactical advice for criminals but it isn't advancing the discussion here.