Fellow students who graduated from Baltimore's prestigious Gilman School can't believe the news about their classmate Luigi Mangione.  The Penn graduate with two engineering degrees is now behind bars in Pennsylvania, accused of fatally shooting United Healthcare leader Brian Thompson outside the New York Hilton in Manhattan last week, just before the company's investor conference.

Freddy Leatherbury, a fellow graduate from the class of 2016 talked to an NBC reporter.  "This is one of the last people you'd think would do something like this, you know he was one of the nicest kids, most friendly kids I had know at Gilman."

It's the same way that longtime Gilman School teacher Liz Sesler-Beckman is feeling. 

Sesler-Beckman retired from Gilman back home to Erie County earlier this year.  During her 15 years at Gilman, she taught Luigi Mangione for two years in middle school.

She said shock isn't enough to describe how it felt to learn that a former student with such promise could be accused of shooting United Healthcare CEO Brian Thompson in cold blood. "It's like a cognitive dissonance between the person that we all knew and the person who would commit such a heinous crime - it just doesn't make any sense and it certainly goes against the values of the school - that we were all part of the community," Sesler-Beckman said.

According to his former teacher, Luigi Mangione wasn't just an extremely diligent student, he was well-liked, involved and rose to be the top in his class of more than 100 elite students. "He was very involved in athletics, a lot of clubs and you know being the valedictorian in a school like that is no -- it's a very difficult task because there are so many superior students," she said, "so I just remember him as always being a kind, well-liked person, I just can't image what drove him to this." 

Sesler-Beckman, who retired to North East to be closer to her family and grandchildren, said her heart goes out to the entire Gilman community as well as the family of the suspect, and the victim.  "There are some kids that you sort of worry about, but he was never one of them, so I'm devastated for the Gilman community, but his family and of course for the victim's family. It's just unthinkable that he would resort to that kind of violence."