It is certainly a big deal for those two adolescent kids. Just imagine what they must be going through right now, going online... And even if he did not have kids, his life was valuable nonetheless. Jodi Arias got life in prison without parole even though Travis Alexander had no kids.
My stance is to give Brian Thompson the benefit of the doubt; maybe his hands were tied and he was sincere when advocating for the cutting of out-of-pocket costs and making healthcare more affordable. Maybe he was truly that evil, greedy monster inside, rotten to the core, but I did not know him, was not in his head and did not attend any of those board meetings. I just can't condone that solution.
As for Mangione... Maybe he's totally innocent and had nothing to do with this, but the way things look... I guess he's the shooter or is not the shooter but was still involved. Maybe he has a solid alibi that may get him off, and the real look-alike shooter is out there somewhere... Just a theory.
In any case, Mangione hasn't exactly expressed remorse... Yet. "Your coverage of this event has been completely out of touch and an insult to the intelligence of the American people and their lived experience." This statement almost sounds like an admission of guilt to me, like: "I killed him to shed light on the lived experience of those who have been harmed by the health insurance system, but your coverage is not depicting that."