To get the shotgun in Hello Neighbor, we will need to be running one of the alpha or beta versions of the game (in the current ones it has disappeared). The mechanics and look of the game have changed a lot from then to now.
The first step is to have the dummy of the teacher, which can be found buried in the cemetery room at the neighbor's house. Once you have done so, you will have to go to the room in the classroom.
To get there, from the room where the tomb was, go out through the door, go up the stairs, and enter the first door on the right, that is where you can find the shark in the alpha and beta versions of the game (by now, the water should be frozen). Go through the door at the back of the room, and you will get to the classroom:
Entrance to the classroomWhen you are finally in the classroom, place the teacher's dummy next to the teacher's desk:
Mannequin in the classroomNow, you will have to complete the mathematical operations on the board. When you are there, pick up the numbers 3, 5, and 8 that are painted everywhere. On the blackboard, there are holes to place these numbers. Put them as they appear in the image, and the shotgun will appear from the air and fall to the ground:
The shotgun is oursIt is worth remembering that Hello Neighbor is a stealth horror game with elements that are directly inspired by the graphic adventure genre of the '90s; games such as The Secret of Monkey Island, Day of the Tentacle, or Loom. Due to these elements, on many occasions, the puzzles have crazy solutions that will make us think for a long time before finding the way to solve them.
It is also worth remembering that Hello Neighbor has artificial intelligence that learns from the user and complicates the game as the user progresses.