The killer wore black. "He was like a ghost," recalled Julianna Blank, a 15-year-old student. "He had black clothes, a black hat and black gloves." He was also armed with a pistol and a pump-action shotgun, and he moved methodically through the Johann Gutenberg High School in Erfurt in pursuit of his victims. By the time his two-hour rampage was over, the gunman had killed 16 people and then turned his pistol on himself. After Germany's worst shooting incident since the end of World War II, politicians, parents and pundits were asking last week how a mass murder could happen in this peaceful 13th-century cathedral city in the state of Thuringia in eastern Germany. "It's the kind of thing you expect to happen in America," said a visibly upset presenter on German television. Police had few clues about what lay behind the shooting. The gunman was identified as a former student named Robert Steinhäuser, 19, who was said to have been expelled from the school in February after forging doctor's signatures on notes to the school to explain his absences. Steinhäuser was hardly the classic loner, though. Popular with other students, he had played handball and belonged to two gun clubs, one called the Police Sports Club. His parents were reported to be separated. He lived with his mother, who works in a local hospital. Police raided his home but found no evidence to suggest what prompted the shootings. "He was a totally inconspicuous individual," said Andreas Förster, 42, a biology and sports teacher. "He was a very calm, reasonable guy who wasn't very brave in sports. When I saw him in front of me, I simply couldn't believe that he's capable of such a crime." One clue to his actions may be that when the shootings took place last Friday, 12th grade students had begun taking the grueling examination known as the Abitur, which is necessary to graduate from high school and go on to university. Students were taking the first test, in mathematics, when Steinhäuser burst in. There was speculation that the shooting was in retaliation by Steinhäuser for not being able to take part. But it was eerily similar to the massacre of students at Columbine High School in Littleton, Colorado in April 1999, when 12 students and an instructor were killed by two socially frustrated teens. Only this time, the targets were teachers. Steinhäuser apparently chose his victims carefully. Students described how he moved from room to room in the four-story school building. He shot a teacher, cast a quick gaze over the terrified students and moved silently down the hall. In the end, the body count was horrific: 12 teachers, two students, a school administrator and a policeman were killed during the siege. Ten people were hospitalized, including at least one wounded teacher, a girl with a minor gunshot wound and students who were injured either jumping from windows or scaling a fence to flee the killer. There was also an enduring mystery: students reported seeing two gunmen during the shooting, and one of the gunmen was reported to have run out the door with other fleeing children. "One of the two followed us to the schoolyard and ran away," said Steffen Holzhäuser. "I didn't see where he went. But not back to the school building." Authorities said they were investigating the possibility of a second gunman but could find no trace of him. German leaders said they were deeply disturbed by the killings. "We're all shocked," said Chancellor Gerhard Schröder. "Any explanation we can give will be insufficient." The killings came during campaigning for national elections in September and are sure to bolster the already hot issue of law and order as one of the main themes of the campaign. Interior Minister Otto Schily, answering questions about school security, said, "I don't believe we can turn our schools into fortresses now. That would be the wrong result." "It was an unconscionable act and unprecedented," said Bernhard Vogel, premier of the state of Thuringia, whose capital is Erfurt. "But it's regrettably not the only case these days." Indeed, within the past three years, three similar, though less deadly, incidents have occurred: In Meissen in 1999, a 15-year-old stabbed a teacher to death on a dare. In Brannenburg in 2000, a 16-year-old boy shot and killed the headmaster of a school from which he had been expelled. And near Munich in February, a 22-year-old jobless man murdered his former employer and the principal of the technical college he attended. Throughout Thuringia church bells tolled dolefully last Friday night, and flags were lowered to half-mast. A day of national mourning was declared for this Friday. Thousands of people crammed into an Erfurt church, where a Protestant pastor and a Catholic priest held a service hours after the shooting. The memorial began with the prayer, "My God, why have you forsaken me?" Protestant vicar Jeremias Treu said he was praying for "those whose body and souls were injured. But also for those who have burdened themselves with guilt." Even a day after the shooting, the scene at the Gutenberg school was palpable with grief. Dozens of students, parents and surviving teachers stood before the 93-year-old building and wept openly. They were hugged and comforted by friends who gravitated to the scene. Mourners left hundreds of bouquets, candles and toys like teddy bears on the school steps. A small blackboard set up outside had a hastily scrawled message: "Thuringia mourns the senseless victims." A student left a farewell letter propped against two candles. It read: "Forget us not your faithful hearts, Stay true far away, without you all the joy is pain, without you all the stars are dark." As students bent to light candles in front of the school, crime scene investigators dressed in white plastic jumpsuits could be seen moving down the corridors of the building gathering evidence. A hastily scrawled sign reading Hilfe — Help — was still pasted in a third-floor window. First word of the attack came Friday at 11:05 a.m., when the school custodian telephoned police and said, "Come quick. There is shooting here." To many students the events that followed seemed unreal. "We were waiting in front of a room for the next lesson, when we heard several bangs," said Denise Hoffmann, 15, a ninth grader. "There is construction work going on in our school, so at first we thought workers had dropped something. But suddenly out of the room, a masked person appeared. We thought, 'This is just a joke,' but then he opened the door to another room and shot the teacher. We thought we were in a movie." The account of 17-year-old Felix Vater was particularly graphic. "Three pupils came into our classroom with shocked faces, saying, 'This cannot be true,'" Vater recalled. "I followed them out and found one of my teachers lying on the floor. At first I said to the others that this was a joke. I felt his pulse and tried to talk to him but he wasn't there anymore. You know the blood from TV, and you just can't believe this is real. There was a second teacher lying three meters away being tended by other pupils. He was still shaking. Shots followed and I said, 'Get out. Get out.' I grabbed my rucksack and ran out. It was only when we were in the schoolyard did we realize what was happening." At 11:12 a.m., the first police car arrived at the school. As the policemen, wearing bulletproof vests, approached, Steinhäuser leaned out of the window and shot one policeman in the head. The officer, Andreas Gorski, 42, was killed instantly. Before he responded to the distress call, Gorski had been preparing to leave work to attend his daughter Caroline's 16th birthday party. "We had a funny feeling when we heard a policeman was killed," said Andreas Ratz, 42, a friend of Gorski's. "We called his wife Kerstin and drove to her house. It was gruesome." At 11:15, a student identified as Maggie managed to make a cell phone call to a local radio station. "We were all taken into a room," she said. "Everybody is crying and all are scared. He shot a teacher one meter away from me and then just looked into my eyes." Julia Schneider, 14, said she heard two loud bangs in a corridor. "The door was thrown open. A man dressed totally in black with a storm mask, a rifle and a pistol shot into the classroom. He shot Mr. Schwarzer, our physics teacher. There was blood everywhere. Everybody cried. Then he pointed at us, didn't shoot, but ran away. We hid in different classrooms. Suddenly, the man in black tore this door open too, pointed his gun at us again and ran away." One of those who responded to the scene was an emergency service doctor named Simone Biereige. She attended the Gutenberg school when she was young and knew most of the teachers. "My homeroom teacher was among the dead," she recalled. "There was blood everywhere, on floors, on walls." She said that Steinhäuser didn't act impulsively. "Everybody who was shot was killed," she said. "Our teacher for German and art just wanted to take our class out of the room," said Dana, a 16-year-old student. "The masked man killed her at very close range with five shots." Confronted in a hallway by history teacher Rainer Heise, Steinhäuser took off his mask and said, "That's enough for today." Heise shoved him into a classroom, where he took his own life. Police revealed that Steinhäuser fired about 40 pistol rounds and had 500 unused bullets, indicating he planned an even bloodier massacre. Manfred Ruge, mayor of Erfurt, said the killings were a careful execution of teachers: "The wounds indicate he was quite selective. He executed them rather than running amok. It shows he planned the entire thing." Steinhäuser's acquaintances expressed astonishment that their friend could be capable of such a horrible crime. "This doesn't fit into the picture I have of him, because he was a very open-minded young man," said Isabell Hartung, a former Gutenberg student who said she knew him well. "I didn't think he was up to something like this. He was insubordinate in school, attracting attention. Students loved it. Everybody got on with him and everybody liked him. I remember that he once told me that one time he wanted everybody to know him and just be famous. This is probably macabre but his dream seems to have come true." Hartung said she doubted the attack was in response to bad grades: "I think the teachers got on his nerves." She described Steinhäuser as someone who was "full of life," meeting friends daily and going to the disco at weekends. Norbert Hieltscher, a fellow member of the handball team, recalled that Steinhäuser had quit the team at the beginning of the season in August 2001. "He said he had too much to do for his Abitur," Hieltscher said. "Nobody thought he was capable of this." Paradoxically, at the same time the grisly shooting was unfolding in Erfurt, the German parliament was in the process of passing new legislation intended to strengthen the nation's already tough weapons laws. But officials said Steinhäuser had obtained his guns legally by joining a shooting club and getting a license from the police. In the wake of this tragedy, the country is likely to ask if the laws on owning a gun are strict enough.