[JAdams]

Don't think it would be a dead ball foul (as Chuck says above), because it's not a dead ball situation. But I would think you'd have to call something. Probably not an intentional foul or a flagrant foul, but maybe an ordinary personal foul. There was hard contact and a player went down, so (based on your description) I think I would have called an ordinary foul. But I wasn't there, so...