I'm all for helping if it looks like an officer is in extremely immediate danger, outside of that I'm going to stay out of it and let the pros deal with it. The last thing I want the officer to have to think about is someone who's background he doesn't know inserting themselves into the situation. If I saw a disarmed/disabled and alone officer and I could help I would, but it's a scary proposition as backup is likely very close and they'll have no idea you're a defender not an attacker.