Police said an autopsy carried out on Tuesday showed that the gunman had shot himself in the head. It was previously uncertain whether the teenager had shot himself or whether the pipe bombs attached to his body had exploded.

At least 32 people were injured in Monday's shooting. One of the school's maintenance men suffered a gunshot wound in his stomach, and three girls and a boy, aged from 12 to 16, were also shot.

Police said none of those injured was in critical condition, although two students were "seriously injured."

The youth, wearing a black balaclava and black gloves, entered his former school on Monday at about 9:30 a.m. CET and began shooting at students.

The 18-year old then set off smoke bombs and retreated to the second floor of the building. Police later found him dead on the floor with two sawn-off shot guns lying next to him.

Police shocked to find explosives

Police found a knife and three pipe bombs wired together on the young man's body.

Five more pipe bombs were discovered in his backpack and four in his car. Similar devices were found in the garage of the young man's home.

The head of the police union, Konrad Freiberg, said the presence of explosions in the school attack added a "new dimension" of brutality.

"It is highly shocking," Freiberg said in the Münstersche Zeitung on Tuesday.

Freiberg said he was outraged that an 18-year old even managed to get his hands on explosives. "We need to explain what type of explosives they are and where they came from."

According to police, the young man's father broke down after learning of the shooting and was taken to hospital. The mother is reportedly suffering from shock.

Web site indicated gunman's despair

The gunman left a message on the Internet that suggested the attack was retaliation for being mocked at the school in the town near the Dutch border.

Police said Web pages showed photos of the teenager holding weapons that appeared to be his own, including a submachine gun.

Criticizing his former high school, the youth wrote, "The only thing I was properly taught at GSS was that I'm a loser."

The message also contained the words, "I hate people," and ended with the words, "I'm outta here."

Teachers in Emsdetten said the attacker had been a loner who often dressed completely in black and wore a long, black trench coat.

According to his former schoolmates, the young man was a fanatical player of the violent computer game "Counter-Strike."

Calls for violent games to be banned

In reaction to the shooting, politicians and teachers warned against increasing violence in films and computer games.

The German Teachers Association President, Josef Kraus, said in the German daily Bild that violent computer games led young people to believe that "the strongest achieve the quickest victories."

"There is no place for the loser," he said.

This sentiment was echoed by the deputy chairman of the Christian Democrats, Wolfgang Bosbach, who called for a ban on violent games such as "Counter-Strike."

"If it really is true that the perpetrator played such killer games over a long period, then lawmakers finally have to do something," Bosbach said.

Four and a half years ago, a former school student of Erfurt's Gutenberg High School killed 16 people and then himself. At that time, violent games and films were seen as possible triggers for the deed.

Bosbach also criticized the lack of school psychologists. In a study of the OECD countries, Germany is in the second-to-last place when it comes to the proportion of students to school psychologists, Bosbach told Bayerischer Rundfunk television.

"Germany is just before Malta," he said.