Somewhere online, I read that the kids usually had their dog with them, but didn't on this occasion b/c mom was aware that some people found the dog scary. That made me wonder if someone had previously spoken to mom at that park about the dog being around the kids? Had the dog ever been unfriendly towards anyone in particular at the park before? I'd be thinking about that if I were LE or involved in this case, because dogs just know. And if a dog knew something on a prior visit, or suspected something or someone of being up to no good? I'd be inclined to follow that up!