Totally speculative, but I imagine it's because of how the events played out. And just to be clear, I have zero experience with law or law enforcement.

Sutton and Zabavsky witnessed Brown committing a crime (riding a scooter without a helmet). They are obligated to perform their duties and stop him from committing that crime. However, their department policy (which as I understand are the guidelines under when, where, and how police officers are allowed to enforce their authority) states they aren't allowed to pursue Brown for that crime alone.

The officers lied to superiors about the events leading up to the crash, and Sutton's attorney told the judge they were making a legal stop to determine if Brown was armed. I'm assuming (because it isn't stated anywhere) it was determined that Sutton and Zabavsky didn't have probable cause to stop Brown for that, and by pursing him they acted outside of their authority.

I imagine the prosecution could argue they were committing a crime when Brown was hit. Again, all speculation.

Fair enough. Legit question; what do you think would've been a more appropriate charge?

So they shouldn't be held accountable when their direct action or inaction leads to the unnecessary death of a citizen?

It wasn't their job to pursue. They did, and someone died. And then they lied about it. How is that any different from vigilantism?

Violating some simple company policy isn't against the law, until the violation of that policy results in the injury, or in this case death, of another person. If the policy wasn't violated and the dude rode into traffic, it would be his own fault. But the officers chased him, so it's their fault.

If you drink a soda at your desk and spill it, after knowing it's against policy, that's willful destruction of government property, which is a crime.

Another note, those police officers not only broke policy and protocol, but lied about it in the ensuing investigation.

It's not like they made a little mistake in the heat of the moment and someone got hurt. Someone died. And they lied about the events leading to his death. Obstruction of justice is a big deal.

Whether it's murder or not is up to the prosecution to prove, which apparently they did.

How is there more risk to the employee outside the store than inside the store?

Sure. But if the security guard wasn't supposed to be chasing the shoplifter, the shoplifter could sue the security guard and Best Buy. Which I imagine is why it's a fireable offense.

Yes. Best Buy's loss prevention policy states employees are not allowed to touch a suspected shoplifter once they leave the store.