It is not illegal to turn over a double yellow line. It is only illegal to pass.
If the driver should have seen the police officer's light, then the officer should have seen the turn signal, after all the turn signal was right ahead, not in a mirror.
While I'm not saying the cop is wrong, I'm also not saying that the other driver was right. I think there is plenty of blame to go around.
The police officer went through a red light and three stop signs without even slowing down; he also crossed the center line several times on a street with no cars parked on it, and a clear straight line. To me, the officer doesn't seem to be in full control of his car.
The other driver should have seen the cop, but cop was going very fast. And he should have pulled over.
I think there is plenty of blame. I also think if it was my house that had been destroyed, and I viewed that video, I would be POed. I wonder if outcome would have been different the man had been sleeping in the living room, as usual, instead of gone. The cop would have killed him then.