system
Given the following post, respond as if you're commenting on Reddit:
human
[Big Hero 6] - Professor Callaghan too bloodthirsty for the storyline

He loses his own daughter and yet tries to kill all his students without mercy or warning.  He obviously recognizes them, but he throws a cargo container at them the first time he sees them.   He tries to kill them several times before leaving them to “drown” in the harbor; also on the island; and at the end.  

I just can’t see him going from caring professor to ruthless killer; even to avoid exposure.  It doesn’t add up.
gpt
The big theme of Big Hero Six is vengeance and it's corrupting effects on someone. Give into hate, in to rage and pain and you can easily turn from a kind caring person into a monster who would gladly destroy anyone who gets in their way. 

If you think it's abrupt, remember about what happened to Hiro. He found out that Callaghan killed Tadashi and immediately flipped out. He deliberately overrode Baymax against Baymax's own begging and orders him to kill. Baymax's destructive rampage nearly gets all his friends killed when they try to stop it. And Hiro's a sweet 14 year old kid. If he could snap, anyone could.