You have to open the elevator, finish the green key/school fear room, lure the neighbor into the elevator and right after he starts climbing jump off and kick him down with the space bar. or "A" key, or "B", or "X"... They added key binding when they patched my glitch. If the neighbor isn't on top of the lost and found box you did it wrong. If he's not in the box at all press the restart button because the game is probably gonna crash. If he's stuck in the floor in the elevator then it also might crash and the chase music won't stop. The gun is not needed but it is useful.