Originally Posted by AZFlyer

Looks to me like the jet rolls forward just a couple seconds after the ramper who was holding up the 'x' to the crew walks away. Perhaps seeing no marshaller holding the 'x' up contributed to prematurely releasing the brakes.

Regardless, definitely some poor communication and some very lucky rampers. Getting pinned between a 60,000lb tug and a 747 would be sure to make your day a lot worse.