SPOILER WARNING
This game was a lot of fun (Or should I say fear?). I love how the twist comes as a sudden shock, but it actually makes sense once you think about it. Why does the PC end up back in the bathroom after taking a manhole... that was inside the bathroom? Because after coming out, she went back to kill everyone. The mirror scene and "blacking out" was foreshadowing some split personality shenanigans. And that's why she was so composed when seeing dead bodies with blood everywhere... because massacres happened all the time, right? The NPC you're supposed to think is the killer is probably a ghost, and even the name of the game makes more sense, the killer is the one pointing and clicking.
Not everything makes sense, but a surprising amount does, which is why I think the twist was really good. The only thing I think could be improved would be if the PC either didn't see a murder happen through her window, or if it were also revealed she was working with other murderers.