Sam would undergo a drastic change throughout RWBY volumes 5-9

Sam's anger (Volumes 5-7)

Context: Sam changes completely after Amelia dies by Marcus' hands, making him more reckless and strict, making his darker side show

Sam snapping at Jack after Amelia's death (Valume 8)

Context: Jack tries to talk Sam down about fighting Marcus and Salem on his own, until he mentions Amelia, making Sam explode with anger and having Ren step in

Sam Blaming Jaune for Ruby's "death" (Volume 9)

(Couldn't find a video for it)

Context: Sam snaps at Jaune and blames him for Ruby's supposed death at the castle, the gang tries to calm him down telling him that she could be still alive, making Sam even more angry showing his dark markings as he snaps on all of them, and hurts Hilary in the process, Sam stops realizing what he's done and runs off crying