After a sketchy, unverified image showing accused assassin Luigi Mangione happily hanging with a group of inmates at the notorious Metropolitan Detention Center in Brooklyn was released — sources tell Page Six that Mangione is indeed a “model prisoner” who’s mentoring other inmates.

“Yes, he’s a model prisoner,” said a source familiar with the infamous facility. “That’s the word from the prison, and people [who] float in and out of the MDC . . . is that, you know, he’s well-liked.”

The source elaborated of the University of Pennsylvania alum, 27, who’s accused of killing UnitedHealthcare CEO Brian Thompson in cold blood in Midtown, has “been very helpful. Helpful to other new arrivals to get acclimated. He’s in general population, and he’s just been very helpful [to prisoners] to sta

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