This advice might save a life.

When you are standing on the side during an altercation involving a cop, just shut the hell up. Words are very intimidating, especially to police officers who are trying to subdue someone. Outcries from the sidelines often inspires the suspect to struggle, which causes the cops to use more force. This type of situation can escalate until somebody gets hurt or killed. Learn self control. No matter what you may be thinking, SHUT THE HELL UP!