Perhaps it would be better to yell "the police are on they" or "they have been called" that would probably bypass any legal problems of being mistaken for an LEO by yelling "Police".
Just following the advice of Mas Ayoob. You aren't identifying yourself as a Police Officer, you are calling for one.
As long as we are here, I'll post my feelings on not getting involved... I've not mentioned it in previous threads where it came up...
Maybe my post on the discussion of the Warsaw Ghetto has it fresh in my mind.
I would probably be asking for a world of hurt and hard times, but I simply could not not get involved if I was in a position to stop further killings.
I could not "get safe" and leave others to die if I possessed the skill and opportunity to to save lives.
A lot of folks in Germany got safe and let the NAZI's take the Jews...and many of them were the Jews themselves.
We have often talked of Wolves, Sheep and Sheep Dogs and picture ourselves as the Sheep Dogs, but the Sheep Dogs don't get safe.
A few days ago, I came across an old post that spoke to a situation where a gunman was robbing a store with a gun pointed at the clerk. The comment was that the poster would not get involved unless the gunman shot the clerk.
I simply could not do that. If someone presents a gun in the commission of a crime, I take that as intent to do serious to fatal harm along with the ability and opportunity. If I have a good shot, I'd take it.
Even though I don't shave any more, I do look at myself in the mirror and I'd not know that I could do that if I hesitated or got safe and the clerk was killed or injured.
Yeah, I'm not a cop so it's not my job, but, for me, it is my moral responsibility.
It might not be the smart or wise thing to do, but, for me, it is the right thing to do.
Let me state that I am only pointing out how I would make my own moral decisions, and not condemning any who would make a different one.