UHC CEO Murder: Person of Interest 'Exceptionally Kind,' Friends Say

UnitedHealthcare CEO Murder Person of Interest 'Exceptionally Kind,' 'Very Intelligent' ... According to His Friends

Luigi Mangione, who has been named a person of interest in the murder of UnitedHealthcare CEO Brian Thompson, has been described as an all-around good guy ... this according to his friends.

Sources close to Mangione tell TMZ ... they don't have anything negative to say about the person of interest -- though, some had some not-so-nice things to say about his family. (More on that later on!!!)

One pal described LM as "an exceptionally kind and compassionate friend" ... and made a point to highlight that Mangione, who attended University of Pennsylvania, is a "very intelligent" individual.

We spoke with another one of Mangione's acquaintances, who revealed he was in the same fraternity as LM -- Phi Kappa Psi -- but admitted they didn't interact too frequently.

Still, the source remembered Mangione as a normal guy ... who didn't have any notable health issues -- which some have speculated could've been a possible motivation in the crime.

While Mangione has had nothing but his praises sung in the aftermath of being named a person of interest, we're told his family has quite a different reputation.

Another person familiar with the Mangione family tells TMZ ... they are very wealthy and well-known across Maryland -- where LM grew up -- as they own several businesses in the state, including various senior and assisted living homes.

According to one ex-employee who worked for the family for over 10 years, they are hard to work for ... with the former staffer noting that they're "very harsh" with employees and expect a lot.

The person says most of the Mangione family is still based in Maryland ... with Luigi being the notable exception to move out of state.

We've reached out to multiple members of the Mangione family for comment ... so far, no word back.

Luigi Mangione was declared a "strong person of interest" in the case Monday in a news conference in New York City ... authorities said he was detained at a McDonald's in Altoona, Pennsylvania after he was recognized by an employee from suspect photos. He allegedly had a gun and a fake ID related to the case, and had a handwritten "manifesto." Thompson, a healthcare industry executive, was fatally shot outside a hotel in Midtown Manhattan early Wednesday morning last week.