My old farm was across from a lake owned by the DNR, so no fishing, no critters were ever disturbed, etc.
From time to time I’d find huge, and I mean HUGE, snappers in my yard who had managed to make it across a relatively busy road.
So happy none of my kids, pets, ME or the free-ranging chickens ever got bitten!
So, I’m going with your Snapper Theory. ;)
Our pastor knew of a family whose son drowned, when a large turtle grabbed his leg, pulled him under, and wouldn’t let go. He was a young teen or preteen, not a little bitty kid. Snapping turtles are ruthless.