Yep.
Had that weight been pushed by any kind of speed, even a big Lexus would have the rear end in the back seat.
At worst this is vehicular manslaughter, which might get you jail in California but likely probation and community service. He will pay out the ass for this though in civil court. Even the people in the Hummer will sue him. His only recourse will be to prove that he was endangered by the papparazzi which would necessitate a reasonable escape.
Wonder if he even had the electric brakes plugged in on the trailer.