The tragic shooting murders this weekend of a Minnesota politician and her husband, and the attempt on the lives of two others, who both survived — was apparently pulled off by a police impersonator. Events like this are ratcheting up distrust between the public and law enforcement personnel … and a former lawman breaks down what this trend means.

Author Steve Lazarus, a retired FBI Special Agent with 22 years on the job, joined us on “TMZ Live” Monday to talk about the effect “guys cosplaying as cops” are having on public trust and safety … and he’s not exactly optimistic.

Lazarus tells us about how destabilizing it is when you don’t always know the good guys from the bad guys … What is the average civilian supposed to do with people impersonating police and other law enforcement officers — like ICE agents — in an attempt to get away with crimes … including murder?

Vance Boelter is accused of wearing a police uniform and driving an SUV made to look like a police cruiser … he allegedly banged on the doors at the victims’ houses early Saturday morning, identified himself as a cop, then opened fire.

Lazarus says he doesn’t have a view into the Minnesota investigation, but he does advise that a single cop is rarely, if ever, going to be alone presenting a search or arrest warrant, for example.

Harvey points out individual cops were going door to door in the Pacific Palisades and Altadena back in January during the raging wildfires in L.A. … Lazarus says it’s definitely context-specific. But when it’s quiet out on a normal night and someone claiming to be a LEO bangs on your door — well, watch the clip for some pointers before opening the door.

Lazarus says it’s not all new … even 25 years ago, working cases in Atlanta, he investigated dope dealers ripping each other off, posing as police to pound doors and do raids at 3 A.M. But it was relatively rare.

He says nowadays, even he and his law enforcement buddies agree — you can’t simply trust that anyone who’s knocking at your door is legit, or has “your best interests in mind,” especially in the dead of night.

The Minnesota shootings — Melissa Hortman‘s death was called a politically motivated assassination by Minnesota Governor Tim Walz and others — adds to the already on-edge feeling people have about cops … heightening the danger to legitimate law enforcement officers, who have to deal with an increasingly suspicious public.