The cops never charged Orlando Anderson with snuffing out 2Pac.

But some of them knew it was him soon after he did the deed during that notorious night in Las Vegas.

That's because multiple members of the Southside Crips were police informants and reported his bragging about the incident, according to LAPD detective Greg Kading.

Kading, who worked the case, also explained that one of Anderson's aunts quickly called the authorities to rat her nephew out. She did so anonymously, but the police were able to figure out who she was. (Later on, Anderson's uncle Keefe D also ratted him out. But Anderson was dead by then.)

As for her motive to turn on her fam like that ...

"She's not from this gang culture, and you start to realize somebody's life was snuffed out," Kading said on Vlad TV. "Not only somebody but a prominent respected member of our own community. And people are going to continue to die if somebody doesn't step up and put a stop to this."

Listen to what Kading has to say on how the police knew so quickly what had gone down.