Make it simple, equal ground rules for police as citizens. If it's illegal for me to point a gun at someone because someone told me a scary, it ought be the same as police. The dichotomy exhibits the standing army effect the founders warned against .

If it's not typical, it should be seen more skeptical, not less. If I say my neighbors are witches who worship the devil, and are going to summon legions of Hell to earth this evening, then the police shouldn't start with burning their house down, with them inside, just in case. They should first try some other means of verifying this highly unusual claim, before acting on it as if it were true. I am reasonably sure the prior of that email being true, based on all previous emails they've received in that police department, is less than 1%. And yet, after that, and after already finding out there's no murder happening on the scene and no emergency at all, they still behaved as if the victim is the criminal. And I am sure they didn't even get politely reprimanded by that - probably they were praised by their peers and their managament for quick and decisive action.

Reasonable articulable suspicion of committing a crime is a bar. Quite low, but "suspicion of committing a crime" is not met based just on an anonymous tip, as SCOTUS said quite clearly. It is enough to investigate, not to arrest and not even to detail someone.