The cruiser did signal before going in front of the jeep.
Looks likely to me that the jeep saw the cop car's signal, and decided to speed up so as not to let the cop get in front of him.
Most motorists have that bad habit. Cars signal for a reason: it's a warning that the car will enter your lane and that the driver hasn't got eyes in the back of his head. Speeding up in response to such a signal is moronic, dangerous, and rude.
It didn't happen that way. Review the video, starting at the 0:48 mark.
The Jeep was in the passing lane and was just about to pass the cop, who was in the lane to the right. It was then that the cop signaled and turned at almost the same time, cutting off the Jeep. The only thing the driver of the Jeep had time to do was brake to avoid an accident.