I took it as his grandpa had the gash on his neck bc the creature TRIED to take his head, but somehow failed? Like maybe someone saw & shot it and got him to a hospital? Bc your grandpa can’t be the monster since it was a female body…and you’re human, right? Plus, your grandpa probably wouldn’t be dying of old age if he was the monster. & why would your grandpa wait until telling you the story to tap on your window? Maybe it knew your grandpa died & came to visit for old time’s sake? Am I totally off?

Although, you did say he was a powerhouse of a man, so….

Edit: ummm, okay. So, I just read the previous story your “grandpa” told, and I’m pretty sure he is the monster. What does that make YOU??