Late to the discussion
Here's my thought,
If you feel that someone is in a life threatening situation it is a question of conscience. When you wake up tomorrow and you could have saved a life but did nothing.
You might have to pur yourself in harms way to get it done, but you will sleep better.
Even if all you have is a cell phone use it. It will get the right people to the scene. Don't let macho B.S. land you in the cell next to the offender.
Lastly, you shouldn't say anything. If you are saying something you aren't in a life/death situation...just my opinion.
Get your facts first, then you can distort them as you please.