Local San Diego TV news reports that a witness helicopter pilot says the accident crew was trying to land on a dolly (news report called it a "portable landing pad"), which had no chocks or brakes to secure the wheels. The dolly was moving about as the accident AC tried to land on it. The dolly moved forward when the skids contacted it and the TR struck the ground.
The recorded TV broadcast showed the TV reporter interviewing the witness pilot who is based at Palomar and knew the two victims. He was very clear about what he saw with the unsecured dolly wheels.
I've seen no subsequent verification of the report during the last 24-hours but it was "BREAKING NEWS" at 11 PM Friday here in San Diego.