"It was Tim," the youngsters quickly told the authorities. "Tim Kretschmer."
The bespectacled 17-year-old former pupil walked into Albertville Secondary in Winnenden, near Stuttgart, at 9.30am on Wednesday armed with a 9mm Beretta he had stolen from his gun enthusiast father and wearing a K4-Schutz bulletproof vest and the black fatigues of Germany's elite forces, the Kommando Spezialkrfte. Former classmates thought the teenager was playing some sick joke – until, without saying a word, he opened fire.
For four hours the youngster was to terrorise the suburbs of wealthy Baden-Wurttenberg, the land in the south-west corner of Germany best known for its high-class spas, woodland walks and Mercedes cars.
He killed nine pupils at Albertville, all but one a girl, and three teachers, all women, in less than 10 minutes. He then shot and killed three bystanders as he tried to escape, before taking his own life after a shootout with police.
Even after a spate of such shootings across the continent, most recently in Finland, and only seven years ago in Erfurt, eastern Germany, most of the pupils were still at a loss to understand what had happened to them. One stood outside his school holding a piece of cardboard on which was written: "God. Where were you?" The local paper took a simpler line: "Warum?", read its headline. "Why?"
Authorities late last week began to think they had something of an answer for the paper. Kretschmer, announced minister of justice Heribert Rech, had left a message on a chatroom the night before he launched his assault on Albertville. He said he was "fed up of his life" and added that "everyone laughs at me, no one recognises my potential". Chillingly, the post went on: "I have weapons here and tomorrow morning I will go to my former school and I will really administer a grilling."
Police, however, by the weekend had come to the view the post was probably a hoax. "Some crazy person obviously put out this dreadful false message," a red-faced Rech admitted. The internet posting, however, did tally with early descriptions of Kretschmer's state of mind in the days and weeks up to the events of Wednesday. It emerged that Kretschmer had been suffering from depression, even attending a clinic and receiving medication for the condition.
The 17-year-old had far from excelled at Albertville. His parents – his father Joerg was a wealthy owner of a packaging firm employing 150 people – had removed him from the state secondary in 2007 and sent him to a private school. His grades were poor and teachers were unimpressed.
The Kretschmers hired a tutor. She felt the boy had problems. "He was a really strange boy – introverted and closed," she told German newspapers. "But he did love his cat."
Kretschmer tried sport – especially table tennis – but wasn't very good. Over the years he became more and more interested in just two passions: violent computer games and guns. The teenager was obsessed with Counter-Strike, a 'shoot 'em up' game in which special forces have to kill terrorists to win. He was good, his few friends said. He was also, they added, a fine shot.
Schoolboy Dustin Schleehaus knew Kretschmer for more than a decade. On German television he said: "In school he was always very quiet. At home he was aggressive, particularly when he was shooting pistols and airsoft guns.
"He loved shooting at targets with his airsoft gun with plastic pellets. He used to do it in the cellar. And he always hit the bullseye – unfortunately.
"At school he hardly ever talked. Sometimes he listened to the teachers, sometimes he didn't, as if he was completely somewhere else. But I still wouldn't ever have imagined he would do something like that, because he was so quiet…
"Maybe his life wasn't perfect. Even though his parents were well-off and he got everything that he wanted. But he generally stayed cooped up at home, he never went out in the evening. I think that he played a lot on his computer, on Counter-Strike. He didn't have many friends. They only really liked him because of his cash."
A 19-year-old from Kretschmer's home village of Leuterbach said the teenager's passion for guns drove away some of his playmates.
He said: "My parents knew his parents. They begged me to play with him because he had no friends.
"Tim had at least 30 airsoft guns on the wall of his room. His father had even built him a shooting range in the cellar. He always shot at us with the airsoft pistol and wouldn't stop. It really hurt! We didn't want to play with him any more."
Kretschmer soon tired of his airsoft guns. Another friend explained: "His father was in a shooting club. He loved his father's Beretta."
Police officers, meanwhile, have begun to wonder if there may have been some sexual motive at play. Most of Kretschmer's victims were women or girls.
Rech, the interior minister, said: "The gunman killed eight schoolgirls and one boy and shot dead three female teachers in the school building. He also injured a further seven schoolgirls. The fact that the vast majority were female victims is notable. The killer shot most of his victims in the head, which shows that they weren't random targets."
There was speculation in German newspapers this week that the teenager had been rejected by one particular girl at Albertville, but it was not clear if she was among the victims. A neighbour said the boy had made misogynistic remarks.
Witnesses clearly thought he was targeting girls, especially in 9c. The dead there included Selina Dogan, Chantal Schill and Jana Schober, all aged between 14 and 16. One survivor, a boy identified only as Patrick S, said: "We were in a German lesson when Tim suddenly came into the classroom. He was dressed in black and armed.
"At first I thought it was a joke. Then he started shooting. He didn't say anything, just fired. There was a crazy amount of shots. My classmates were falling down around me.
"We pushed the desks over and hid behind them. I suddenly realised I had been shot. In the back, arm and cheek.
"All of a sudden he was gone. We then barricaded the door. And then I saw my classmate Chantal. She was sitting at the door – dead."
Another pupil in 9c, a 14-year-old girl called Selina, told German tabloid Bild she was sure Kretschmer was looking for girls. She said: "I was sitting at the front of the class but saw him as he came in the door at the back. He started shooting.
"I threw myself to the ground and pulled my friends down with me. We tipped the desks over and hid behind, screaming. I saw that Jana, who was sitting two rows behind me, had been hit – blood was coming out of her nose but she was still sitting at her desk.
"Later she fell to the floor and a lake of blood formed around her. She was still twitching – it was awful.
"Our classroom used to be 10d, which was Tim's classroom when he was at the school. Maybe that is why he came to us – it still says 10d on the door."
The 14-year-old said her teacher, Ms Braun, helped shut the door as Kretschmer went outside to reload. He shot the woman through the door, hitting her hand.
Other members of staff were not so lucky. Three, all women, were found dead. Their bodies, witnesses said, blocked doors. They had tried to put themselves between Kretschmer and their charges.
Germany has strict gun laws. Police were yesterday understood to be considering whether they would be able to charge Kretschmer's father with any offence. As the registered owner of 14 weapons, he was supposed to keep them secure.
There was little debate about further tightening the law. Some politicians renewed calls for metal detectors at schools. But others pointed out that the system had protected some children. Kretschmer, they said, could have killed far more people. He is believed to have fired just 100 of his 600 rounds of ammunition.
The school's principal, moreover, was able to evacuate pupils quickly using a secret codeword. "Frau Koma is coming," he announced over school loudspeakers, telling staff to get their pupils out.
The Greens and Social Democrats in Germany called for more training for teachers and more psychologists in school to help spot the symptoms of a potential killer sooner.
One friend, meanwhile, suggested Kretschmer may well have been inspired by the killing of 10 people in Alabama the day before he picked up his Beretta.
The friend said: "He liked games like 'Counter strike'. It wouldn't surprise me if he spent the whole night before the spree on his computer playing games, heard about the shooting in the USA in the morning – and then went to school."