I've not read or seen any interviews of the driver, there's some stuff out on the internet and a lot of rumors. But basically he's and the car in front of him got there before the police could shut down the road behind them. They let the car in front of him pass and when he started to move they jumped in front and essentially tried to hold them there against their will.
Guess what, that's illegal and when he tried to move forward they banged on his vehicle and threatened him. So he moved forward and they got out of the way.