(Don't even bother w the movie </3 I'm just weak to men in gas masks)
The prank was doomed from the start. If it even qualifies as a prank. You'd only tagged along to the abandoned chemical factory as moral support— for Jacob or the girls. What kind of messed up idea is "scaring him into being normal" to begin with? The show in charge of this is messed up in it of itself.
Maybe Jacob's a bit odd in how his eyes sparkle when he talks about the history of the factory— the one his father died in— and how he blatantly stares at people he likes, but he doesn't deserve this. This point is only drilled into you as the fun little prank rapidly turns into a fight for survival.
Somehow Jacob got ahold of a hazmat suit, a gas mask, and an axe. Somehow the revenge appropriate for the prank planned was death. He maimed his friends - your friends. Until gradually the time came he found you, too. But like with Melanie, he hesitates. Axe still grasped tightly in his hands even as he tilts his head almost curiously.