After reading the article... Yes its was illegal.
As I understand the law, after reading "Florida firearms, lawful use and ownership" that was written by a gun lawyer. (Im not a lawyer, but ive read this book a few times to verify that im legal in EVERY WAY as I carry concealed at times.)
If he had shot the coon as it was attacking chickens then it would have been legal.
But when he drowned it after the fact, then his property was not in immediate danger.
He killed it out of revenge. FYI: I would have done the same, im not condemning.
My silencer cost me 600 bucks on silencer shop.com.
My .22 pistol that is silencer ready was 400 bucks.
I didn't buy it for this, BUT. For 1k, you can handle situations like this quietly.
Unlike large caliber pistols, a .22 can be so quiet that you can hear the action cycle.
1 thousand bucks, and you will never turn a eye. FOREVER. Seems like a investment to me if you have coon problems, and a nosy neighbor.