Need the OTs help.. Might be in some deep legal trouble

So about a week ago my son had a friend over and any time a friend comes over I force them to play outside just like whenever I was a kid. We live on a large piece of property so it is not unusual to see all types of wildlife (snakes, racoons, nutria etc). I have taught my son how to safely dispose of snakes with a shovel and i am fairly comfortable with him doing so. Long story short my son and his friend came running into the house saying that they found a cotton mouth near the edge of the pound while they were fishing. I gave my son a hatchet and told him to just take care of it. Minutes later my son comes running back into the house saying that his friend had been bitten. After the kid spent a couple days in the hospital, many viles of anti venom and almost losing his foot the kid is mostly okay except for a little nerve damage.

Now the other kids family is absolutely pissed and threatening to sue, Now I believe me and my son did nothing wrong and if the kid felt uncomfortable he should have removed himself from the situation. How screwed am I?