For this achievement you'll need to blast ONE coffin that is flying from the background during the Central Park Cemetery chapter at the "Airstrike" checkpoint.
At the beginning of the checkpoint the coffins will begin flying towards you. You'll be able to spot them by the small flaming trails. Three will fly at you at the beginning. The first two are paired closely together and will roughly land on your head. So you can simply aim straight up to hit one of those with your basic photon stream. If you're waiting for the third you'll need to move forward and aim up to your right about 2 o'clock. If you aren't able to hit a single one of these three coffins I recommend reloading the checkpoint because by then enemies will have spawned and it will be too hectic to focus on hitting another coffin.
Good luck.