The people who watched the helicopters weren't doing anything criminal, that's why they can't be held accountable. When you invite a friend over, you're not doing something criminal, that's why you can't be held accountable. And whether or not a house owner (whose house is burning) is responsible depends on whether he had a criminal intent (arsen). But the driver? He was evading the law, there was criminal intent.
What if as the driver was running from the police, a bystander driver had to swerve to avoid the criminal, and ended up crashing into another bystander? Is it the bystanders' fault, or the criminal driver, who didn't actually hit anyone?
The point isn't to say that this driver is accountable for specifically 4 people's lives. The pilots have their share of responsibility, and they've already paid the ultimate price for that. But these deaths have to be rationalized somehow (think of the news crew's families), and the only reason they were out there in the first place was because of the driver. I'm not saying the driver deserves 4 counts of manslaughter, but I wouldn't be surprised if he is held partly accountable for the accident.