The scene could very well be a father with an uncooperative child, or a kidnapping.
The fact that the other parents aren't doing anything is irrelevant, as people in general don't mix up in anything that doesn't immediately concern them.
I think I'd approach the man, and politely ask what the problem is. If he gets red-faced and starts yelling, then he's probably the kid's dad, and doesn't appreciate interference from some nosy bastard. If, OTOH, he's a goblin, he'll likely run like hell.
IMHO. YMMV. IANAL. TANSTAAFL. TLA.