Looks like the first volley of fire was from the inside of the truck directed towards the officers...rate of fire looks a lot like full auto, or at least very fast trigger work.
The thing that always amazes me in these situations was that no one on the opposite side of the freeway traffic was hit by stray rounds. Also, feel free to close off traffic from the other direction, either Phoenix PD or DPS. I know these situations are fluid and it can be difficult to judge where the PIT maneuver was to be attempted, but a little collaboration with local PD would be helpful.