without a photo or better description of your setup, i am going to guess that you were using chicken wire to enclose your chicks.
chicken wire is very good at keeping chickens in.
it is useless at keeping predators out.
secure the birds you have left with no gaps or openings. lock them inside at night. dont leave any poop doors open. the raccoon will continue to return now that he has found a place offering tasty morsels.
i dont think you should sit outside most of the night with a loaded gun. especially since you are in Pennsylvania.
instead use time to secure your coop. also live traps might work if you use one of your dead chicks. WIRE it in the back or right on the Pan. if this is the raccoons only food available he just might go for it. if you already disposed of your dead birds, use raw chicken leg, a can of tuna, or something they will like. again Wire it so they HAVE to go inside to access it. place the trap on a level surface....test fire it a few time to KNOW that it is working correctly. if i could i would place it in the same place that he killed your birds. he will return there first. or as close as you can to that spot.
if you do Trap it..Kill it.
some folks will relocate "the poor thing" moving their problem to some other chicken owner resulting in more tragedy like yours.
sorry about your birds.. it is heartbreaking when this happens.
Remember:
1/4 inch hardware cloth...Good.
Chicken wire...Bad