It was just twitching while dead. Last fall I was walking around my FIL's farm and had my .41 mag on my side. Was hoping to see a hog but ended up spotting a coyote about 30yds away. I put one round (iirc I had 280gr cor-bon hunting slugs in it) through the yote's head. It bounced in the air then twitched for 30 seconds or so.
Just the nature of the brain shot.