Responses
Either
a) he had killed him b4
b) he's only found out that the grandpa got in btw him and mc, so now he's hella mad enough to dig up the grandpa from his grave (who had presumably passed long ago to reasons unknown to us) and kill him :)
WAIT WHAT DOES THAT PSYCHO MEAN BY DUGGING ANG KILLING HIS GRANDFATHER AGAIN BY HIMSELF????????? ANYWAYS BLUE HAIRED DUDE'S CUTE IN THE LAST PANEL