The cop car was clearly at fault here. No turn signal, didn't check if lane was clear. No debate there. The guy is also seriously injured, which sucks.

But, at the risk of sounding like an a-hole: it does seem, as some of the youtube comments also point out, that he was trying to catch a light he probably wouldn't make. (specifically, you can see him speeding up when it turns orange. I don't know the US laws, but in the Netherlands, orange means "stop if you can").

It also seems like he's not really paying attention at that point, between the cop car moving and him hitting it, there's a full 2 seconds. Had he been paying attention to the cars he's passing, I would have expected to see at least an attempt to swerve/brake.

My conclusion (which is based on a youtube vid and could be completely wrong) is that while the cop is at fault here and should be held responsible, safer and smarter cycling could have prevented this accident. It sucks that you have to basically always prepare for idiots on the road, but still, that's the way to prevent most accidents).