Be weary when interviening in a situation you do not know. When I was young it was very costly to one of my uncles.
We were at a Taco Bell late on a friday night in the drive thru. We saw the scene of a man who had grabbed a woman by the arm, and slammed her on the car. She was yelling for him to let her go. My uncle grabbed the shotgun off the window rack of the truck and went to help the lady.
Within a couple of seconds there was a parking lot full of police cars, and my uncle was at gun point. He was arrested, and charged with a slew of charges. Turns out the man was an undercover narcotics officer, and woman had made a sale to him. He was arresting her. It just took a bit for the back up to arrive.
All charges against my uncle were dropped. It still cost a whole lot of money for bail, and the attorney.
Oh and his shotgun was returned.
It could have turned out very badly, the respoinding officers showed a lot of restraint, or else the story would have been tragic.
No matter how many times you do it and nothing happens it only takes something going wrong one time to kill you.