This video took place in Grand Prairie, TX USA on 5th May, 2017.

Here's what we think happened. As the video first begins, the southbound (right to left) and northbound (left to right) lanes all have green lights. Just prior to the northbound car beginning his left hand turn, the northbound traffic lights go yellow (0:05). Because the southbound traffic had stopped, the driver likely assumed that the lights in all directions were transitioning to red, and this was an opportunity to go before full red light.

In actuality, the southbound traffic has stopped because of the traffic backing up towards the intersection. The southbound traffic lights remained green. The northbound lanes were only turning red to give the southbound turn lane a protected left turn arrow.

It doesn't appear that the initial police car had its emergency lights on and the police SUV doesn't turn on his lights until a few seconds after the accident. With this in mind, I do not believe that the traffic signal preemption equipment on the police vehicles had any impact on the intersection light timing prior to the accident.

The accident appeared minor with no injuries.