Questions (spoilers)
How come Baymax had to sacrifice himself for the fist to work? Also, was what happened to Tadashi murder? Was that fire planned?
share1) Baymax was a gonner already. Firing his fist was the only way to get Hiro out.
2) I would say second degree murder. It was not the intent of Callaghan to kill anyone. Only to stage his own death and get away with the micro-bots.
3) I think Callaghan thought of this in the moment. When he realized he could use the micro-bots to get back at Krei.