Seems a little cruel to me. If you can't kill it humanely just drive somewhere and release it.
If you shoot a raccoon you may be able to make someone happy in some neighborhoods. Just give it away.
Last year there was a guy in Metairie arrested(discharging a firearm)for shooting a possum behind a bar in the dumpster.
OP is in Orleans Parish, I believe. Illegal to discharge a slingshot in Orleans, much less a firearm. Releasing it elsewhere just makes it someone else's problem. Not the neighborly thing to do.
Clubbing it to death would probably be more cruel than drowning.
Drowning is quick, clean and quiet.