This one isn’t so straightforward. Not a liberal or conservative thing, either.
First, though, if one calls the police in the Medina Shel Chesed with a bill of rights and the rule of law, is it still mesira? Not so straightforward.
Second, on the other side. Yelling and screaming doesn’t necessarily constitute “raglayim ledavar”, so either waiting until you have a clearer picture or asking a competent, aware, and unblinkered halachic authority for advice could be a good idea. That is, unless you hear someone say “I’m going to kill you” or something like that. Then asking your Rov or waiting for more evidence is indeed standing on the blood of your neighbor.
Third. Speaking to a Rov doesn’t necessarily mean you are asking a shailah which you are then obliged to adhere to. You can ask for advice as to what should inform your own decision making from a halachic POV, you can ask quite a bit that isn’t “tell me what to do, please”.
My personal opinion, all of this being said, is to be near certain you have cause for alarm before calling the police. Use your head. Ask a Rov for guidance or advice if you must, but YOU are hearing or seeing this, not someone on the other end of the phone. It is unfair to that Rov to expect him to make the best informed decision about the situation based on secondhand “evidence”. And finally, if you are convinced that someone is being endangered, don’t call hatzolah. Call the police. When HKBH calls you to account for it there might well be a saved life on your account to balance any possible halachic breach.