The police were outnumbered, and walked into what, by all accounts, was a volatile situation.
They had no idea what was going on, or who was to blame, so they took out the apparent "leaders" in order to break it up.
It's important to understand what this looked like to them. Wars get started this way--don't be part of that.
The way you see the police in this is exactly how the people in other countries see our "police actions."
What do you think? http://consequeries.com/