Key words to use if you really want a policeman.
That doesn’t always help. There was a recent incident in Garland where a crazy man with an illegal AK rifle kicked in the front door of a random apartment and started shooting. The neighbors called 911, the police took over 10 minutes to get there. By then, the inhabitants (a dating couple, I believe) had actually successfully executed a fighting retreat with their handguns. While the couple were wounded and had been driven out of their home, the nutcase was dead.
Of course, the police didn’t get there until it was all over.
Keywords to use if you REALLY want a policeman, “I think he shot an officer!”.