On the day of the shooting, before leaving his residence at his usual time, Steinhäuser armed himself with a 9mm Glock 17 and a Mossberg 590 Mariner 12-gauge pump-action shotgun, which was unusable due to an earlier handling error. Steinhäuser probably entered the school unmasked at 10:45, carrying his weapons and ammunition in his sports bag or backpack at the time. He went into the men's toilet on the ground floor and changed some of his clothes, including a black face mask. He left his coat, wallet and identification.