Witch Game 5 - The Anniversary

[Submachine]

Stanley or someone else visiting Stanley's room had previously opened the window. Stanley's killer threw a grendade (or other explosive device) through the window and  killed Stanley, and then Natalie closed the window.

No explosives were involved in Stanley's mystery.

I don't want to pull cheap tricks, so I might just say that the guestroom windows have a self-closing mechanism.

[Fippe94]

Stanley or someone else visiting Stanley's room had previously opened the window. Stanley's killer used the stolen harpoon gun to be able to climb the outside wall to Stanley's room. The killer shot Stanley from outside the window with some ranged weapon, and then closed the window and climbed down again.

[Submachine]

Stanley or someone else visiting Stanley's room had previously opened the window. Stanley's killer used the stolen harpoon gun to be able to climb the outside wall to Stanley's room. The killer shot Stanley from outside the window with some ranged weapon, and then closed the window and climbed down again.

Stanley wasn't shot through the window. This includes all kinds of ranged weapons.

There you have it. The climax truth of Stanley's mystery.

[Kuroaitou]

Stanley or someone else visiting Stanley's room had previously opened the window (or propped the window open to keep it from self-closing). Stanley's killer used the stolen harpoon gun to be able to climb the outside wall to Stanley's room. The killer stabbed or attacked Stanley from outside the window with some weapon when Stanley got too close to the window, and then closed the window and climbed down again.

[Submachine]

Stanley or someone else visiting Stanley's room had previously opened the window (or propped the window open to keep it from self-closing). Stanley's killer used the stolen harpoon gun to be able to climb the outside wall to Stanley's room. The killer stabbed or attacked Stanley from outside the window with some weapon when Stanley got too close to the window, and then closed the window and climbed down again.

This is actually a really clever idea and it would create an awesome mystery in a future game.

But sadly, Stanley wasn't killed at close range.

[Fippe94]

Natalie opened the door to Stanley's room, and Stanley's killer shot Stanley with a ranged weapon through the open door.

[Fippe94]

The killer shot Stanley through a hole in the floor, ceiling or wall of Stanley's room.

[Submachine]

Natalie opened the door to Stanley's room, and Stanley's killer shot Stanley with a ranged weapon through the open door.

This past truth seems to counter it:
Natalie didn't let any killers in or out of Stanley's room before you found him.

But just in case: Whenever Natalie opened Stanley's door during the story, nothing harmful went through the door until it was closed again.

[17:16:18] ‹Fippe93› ‹@Submachine› Also, can you confirm, "The only ways to enter or exit Stanley's room are thorugh the door or through the window"

The only ways to enter or exit Stanley's room are through the door or through the window.

EDIT: [17:17:20] ‹MeowMeowCat› ‹@Submachine› The killer is MeowMeowCat.

You got me. It was you all the time.

[Kuroaitou]

A wire of some sort was placed through the door or window at some point when Natalie entered (or before or after). When Stanley got in contact with the wire, he was electrocuted and was subsequently killed.

[Fippe94]

Stanley's killer shot Stanley through a hole in the door.

Stanley's killer opened the door without a key (with a lokpick for example) and then shot Stanley through the doorway.

Stanley's killer removed the door, shot Stanley through the doorway, and then put the door back.

[Submachine]

The killer shot Stanley through a hole in the floor, ceiling or wall of Stanley's room.

The trick will be simpler, but less obvious.

Stanley's room has solid floor, walls and ceiling. Things can only enter or exit through the window or the door.

A wire of some sort was placed through the door or window at some point when Natalie entered (or before or after). When Stanley got in contact with the wire, he was electrocuted and was subsequently killed.

Stanley's death was directly caused by a gun of some sort.

[Submachine]

Stanley's killer shot Stanley through a hole in the door.

Stanley's killer opened the door without a key (with a lokpick for example) and then shot Stanley through the doorway.

Stanley's killer removed the door, shot Stanley through the doorway, and then put the door back.

I already countered the first one.

By the way, When Stanley died, the door was locked. There is no way to lock a door between a bullet being fired and it hitting something.