Warhawk

Have player 2 grab a jetpack and hover in the air. Player 1 needs to obtain a sniper rifle. Simply snipe Player 2 as they're hovering. You can get this trophy and Safety Violation at the same time. Just have both players obtain jetpacks. Player 1 needs to fly to the top of the crane in Tau Crater and stand on the very edge. Player 2 can just hover in the distance near the crane. Once Player 1 snipes Player 2 from this position both trophies will pop.