Gene splicing between humans and hyenas (just hear me out)?

Okay, so I've had this idea whirling around in my head for a while now, and I really want to write it but... I have a problem.

The general idea is that this girl who lives on the edge of a national park (like I do; always base my settings on the place that I live so that they're as realistic as possible) gets angry and storms out of her house and into the woods. She's seriously pissed and doesn't know where she's going and ends up lost, hurt, starving, and completely alone. She stumbles upon this abandoned lab that's mostly underground but for a few narrow windows. It's late fall and getting dark, so she slips inside through a broken window and takes shelter. (I realize how stereotypical this sounds, but I haven't REALLY nailed down the beginning yet. Because I'm smart like that, you know? Ugh)

Anyway, inside she meets a forgotten test subject: a mutated boy with fangs and claws and speckles on his skin like the dark patches a dog has under its fur (among other unusual features). The idea is that there was a rabies epidemic a couple decades ago, and this lab was doing illegal human experimentation. Hyenas are immune to rabies, so they were messing around with hyena genes in an attempt to isolate the strand of DNA that makes them immune and splice it with human DNA. This boy was their creation. They abused him and drove him to madness until he ended up slaughtering all of the lab techs. The only ones left panicked and fled, leaving him to survive alone in the depths of a protected forest.

But... yeah. I am horrible at science and still can see how illogical and ridiculous that concept is. And it's bothering me, because I really like the hybrid-boy character and his role that he would play in the story (he ends up being killed in the end). However, I want to be able to use him in a sci-fi way, not a fantasy way. Do you have any ideas? Or could a reader suspend belief enough to enjoy the story despite the fact that it's pretty much impossible? Thanks.