The missing link: are computers to blame?
With a mask over his face and several large weapons by his side, the figure moves from room to room, gunning down the enemy and leaving a trail of devastation in his wake.
A particular favourite of the 19-year-old killer was the popular 'Counterstrike' - a game in which teams of terrorists battle against teams of police officers.
Such revelations about what Steinhaeuser got up to in his spare time have left politicians and large sections of the German media in little doubt as to what fuelled Friday's killing spree, the worst of its kind in the country's postwar history.
"Software for a massacre," ran the Frankfurter Allgemeine Zeitung headline.
"The killer was trained by a computer game."
Censorship
Edmund Stoiber, who will lead the conservatives into this year's general elections, has called for an immediate ban on such pastimes.
Keen to shake off allegations of negligence from the opposition, members of the ruling Social Democrats have proposed an overhaul of the laws regulating the sale of computer games, and have advocated fresh restrictions on the portrayal of violence in the media.
Chancellor Gerhard Schroeder has called the heads of the country's top national broadcasters to a meeting to talk through the issue.
His spokesman said the discussions would examine whether new legislation was needed to curb the amount of violence shown on television, or whether voluntary regulation would suffice - a development anti-censorship groups have viewed with alarm.
"The country is desperately trying to work out how what happened last week was possible - how one young man could do what he did," Professor Werner Sacher, a professor of education at Erlangen-Nurenberg University, told BBC News Online.
"But it's far too simple to point the finger at the media. I am not an opponent of some regulation, but we shouldn't forget that young people can tell the difference between fact and fiction, and should indeed be given the opportunity to do so."
Playing the game
A community of Counterstrike players has meanwhile launched a website - Gamers Against Terror - and a petition in condemnation of Steinhaueser, and in defence of their hobby.
"It is understandable that the world is looking for reasons and for motives, but it is not acceptable," they write, "to portray us as if we are all lining up to burst into schools, shoot down teachers and police officers and rob old people."
One Counterstrike group has however cancelled a meeting scheduled for next weekend, when 2,000 players were due to gather in Erfurt for a big game session, as a mark of respect for those who died in last week's bloodbath.
But this decision does not mean Counterstrikers are bowing to the pressure coming from Berlin and the media, organisers insist.
"The fact is that 90% of killers have eaten bread before their crime."
"Should we therefore ban bread?"