That's not a "professional" hit! Guaranteed the killer personally knew the shooter! Though cold blooded and deliberate, it seems emotions are involved here! Jealousy, etc.
Fuck, I tell ya, people need to be more aware of their surroundings. Anyone watching the hitman walking up could have yelled, got them up and moving. It might have thwarted the situation. But fuck, they'll never learn. Serves 'em right. Fucking kill them all.