You do not have 1 big snapper. If you have 1, you have many. They are mostly nocturnal and a small percentage enjoy sunbathing or just taking in the sights during the day. They are devastating to small and mid-size life on your pond. Some will live in a hole or under a rock 50 yds from your pond and visit the water every night to feed. It may take years of trapping pressure to rid them from your pond as they will migrate in from surrounding areas. Yet my 100' X 80' pond is snapper free. Dad and I cleared a 3 acre pond of snappers when I was a kid.
I agree with the expensive pcp air rifle setup. Benjamin has a marauder; great value. A 22 rifle with subsonics works well, be safe about bullets glancing off water surface. Snipering requires a lot of time. If you're retired, or young with the summer off, it's a satisfying accomplishment. You'll think they're gone, but the surviving few simply got wise and a week later you figure out there's more still in there. Occasionally a head shot will kill right there, just know the kill zone is peanut size. Nevertheless, nature is cruel and it's our job to manage (ie; lessen) the cruelty.
I found it necessary to eliminate 'em to keep from losing and having maimed ducks.
Trapping snappers is more efficient than shooting. Dad and I always trapped out the snappers cause they destroy the fishing. Just make or buy most any turtle trap and put in fish remains. They crawl up, fall in, can't get out.
https://www.amazon.com/Tomahawk-404R-Trap-Turtles-