On the day of the shooting, Steinhäuser armed himself with a 9mm Glock 17 and a Mossberg 590 12-gauge pump-action shotgun, which was unusable due to an earlier handling error, before leaving his residence at his usual time. When he entered the campus, he went into the lavatories to change his clothes, and then donned a black ninja-style outfit.
The shooting started at approximately 11:05 a.m. Steinhäuser had moved from classroom to classroom, pausing briefly each time in the doorway to shoot the teacher, then moving on to the next room. According to students, he ignored them and aimed only for the teachers, although two students were killed by shots fired through a locked door.
Five minutes after the shooting began, police arrived outside the school. Soon after, Steinhäuser aimed from a window and fatally shot a police officer in the head. Before he committed suicide, he was confronted by one of his teachers, Rainer Heise, who walked into the demasking shooter. Pausing, having established deep eye-contact with Steinhäuser, he said, "Du kannst mich jetzt erschießen." ("You can shoot me now."), Steinhäuser is said to have answered, "Herr Heise, für heute reicht's("Mr. Heise, enough for today"). According to Heise, he then talked to Steinhäuser for a short amount of time, luring him into the doorway of an empty room. When Steinhäuser was in the doorway, Heise pushed Steinhäuser into the room and quickly locked the door. Steinhäuser committed suicide shortly after and his body was found by police a few hours after the shooting. 71 rounds were fired throughout the whole series of shootings.
Steinhäuser's last words -- Für heute reicht's ("It's enough for today") -- was also the title of a very controversial book about the massacre written by Ines Geipel, who alleged that there were several mistakes made by the police on the case. Geipel, and relatives of some of the victims, criticized police for the initial speed of their response. The police had initially believed there was a second gunman, leading them to retake the school one floor at a time rather than storm the entire building.
Heise was touted as a national hero for locking Steinhäuser in a room which ended the killing spree, but was later subject to innuendo and other backlash from some members of the public.
The massacre led to the development of a code word that could be broadcast over the public address system to warn teachers of a shooting. "Mrs Koma is coming", which is "amok" spelled backwards, was later used at the Albertville school shootingto instruct teachers to lock doors.