The Myyrmanni bombing took place on October 11, 2002, in Myyrmäki, Vantaa, Finland, in Greater Helsinki, at the Myyrmanni shopping mall. A bomb hidden in a backpack exploded in the center of a shopping center killing seven people including the bomber. The blast left a 10-cm deep crater in the floor and blew out the glass dome of the mall. The dead included two teenagers and a seven-year-old. 159 people were injured, including 10 children. 66 victims required hospitalization while the remainder were treated and released at the scene. The bombing took place during the pre-weekend shopping surge late on a Friday afternoon, with 1,000–2,000 people in the shopping center, including many children who had come to see a clown performance.
The bomb carrier was Petri Erkki Tapio Gerdt (April 17, 1983 – October 11, 2002), a 19-year-old chemical engineering student at the Espoo-Vantaa Institute of Technology (EVTEK). Described as quiet and somewhat withdrawn, Gerdt was an amateur bomb-maker with no known close friends. He participated in basketball and had no prior criminal record. Gerdt died in the explosion he caused.
He was also an active member of Kotikemia (lit. "home chemistry"), an online forum for amateur chemists. The moderator of Kotikemia was acquitted of responsibility in court. The explosive device was likely constructed in Gerdt's apartment. It was a 1.5 liter plastic bottle that contained ammonium nitrate and nitromethane with shotgun pellets and weighed about 2–3 kilograms (4.4–6.6 lb). Investigations revealed that some kind of timer was also used. Kotikemia was shut down by the authorities following the bombing.
The site of the explosion was at the central square of the first floor of the Myyrmanni shopping centre about 45 metres from the southern entrance near the Iskostori square, next to a McDonald's restaurant, a Musta Pörssi store and a K-Citymarket grocery store. There was a twisting stairway at the site leading to the upper floors and down to the parking garage. The escalators leading to the second floor were also located nearby as well as the elevators. The explosion was so powerful that it broke the ceiling structure, which were damaged but did not collapse. The worst damage was to a relatively small area of about 400 square metres. Traces of the shotgun pellets in the bomb were found inside the shopping centre at a maximum distance of 70 metres from the site of the explosion, near the northern entrance next to the Paalutori square.
The Finnish National Bureau of Investigation investigated the event as six accounts of murder, one account of aggravated criminal mischief and one account of an explosives offence. The case was closed in January 2003 without any indictments as Gerdt was the sole suspect. Gerdt's motive for the bombing was not ascertained during the investigation. There was no evidence found that Gerdt had links to any outside groups or to any international terrorist organizations.
Gerdt's parents went to work at the morning as usual and didn't notice anything strange in their son's behaviour. Gerdt left home from Tikkurila in the morning before noon. He left his mobile phone powered off in a shelf, where it was later found by the police. He also left his computer powered on, on standby.
12:12: Gerdt boarded a bus on line 84 travelling between Tikkurila and Mellunmäki. The investigation did not find what he was doing and where he was going during the next four hours. There has been speculation that he had hid parts of the bomb supplies in forests near Mellunmäki and also worked on his bomb. There are World War I era fortifications in Mellunmäki where it is easy to hide objects into. Gerdt also possibly visited Itäkeskus or other places in Helsinki with the Helsinki Metro.
16:10: Gerdt boarded a bus on line 84K at the Mellunmäki metro station and returned to Tikkurila. He probably never returned home after this.
17:10: There was a confirmed sighting of Gerdt at Asematie in Tikkurila. An eyewitness saw Gerdt walk towards the Tikkurila railway station and the bus station next to it.
17:15: Gerdt boarded a bus on line 50 or a bus on line 55 at 17:18. Both of them travelled from Tikkurila to Myyrmäki.
18:00: Gerdt arrived at Myyrmäki. There are no confirmed records of his movements between 18:00 and 19:20.
19:00 to 19:20: There are eyewitness sightings of Gerdt at Myyrmanni and near it. He went to the public toilet on the second floor to work on his bomb. A ten-year-old boy saw him work on his bag and shotgun pellets from below the toilet stall door. The boy first thought the noise came from a belt buckle hitting the floor, but later realised it had been the shotgun pellets.
19:20: A security camera made the first confirmed recording of Gerdt at Myyrmanni. However the cameras did not record the site of the explosion.
19:30 to 19:35: There are unclear eyewitness sightings about Gerdt's movements. The bag containing the bomb was by his legs at this point. In front of the nearby McDonald's restaurant was a clown dealing out balloons, played by a volunteer employee of the Project Hope foundation. There were plenty of children watching the performance. According to criminal investigation, the bomb was on his lap when it exploded, about a metre above the floor, with Gerdt standing up at the time of the explosion.
19:35: The bomb exploded in Gerdt's lap, killing him instantly. Gerdt's body was flung out a distance of 15 metres and smashed against the window of an Intersport sports equipment store. As well as Gerdt, the bomb killed six people and wounded hundreds of others, some of them severely. The first emergency call was made at 19:36:49. Immediately after the explosion, the shops at Myyrmanni were closed and the intact survivors at the shopping centre were guided outside. There was no real panic at the shopping centre according to eyewitnesses.
19:38: The first emergency rescue units arrived at the scene. According to first information, the explosion was thought to have resulted from an exploded gas bottle at the clown performance. The first police patrol that arrived on the scene found Petri Gerdt's driving licence on the floor near the check-out counters at the Citymarket grocery store. The licence proved to be a conclusive clue and was sent to the Tikkurila police station and from there to the Finnish Central Criminal Police. A total of 59 wounded, of which eight were children, were transported by ambulance and Medi-Heli helicopter to the Töölö, Meilahti, Jorvi, Peijas and Hyvinkää hospitals as well as the Children's Clinic Hospital, and during the next four days 27 patients were operated in 49 operations.
20:04: The Finnish News Agency STT published the first news about the explosion at Myyrmanni. YLE made a special broadcast about the event.
20:50: The last wounded patients had been transferred to hospitals. Criminal investigators arrived at the scene. As the explosion hinted at terrorism, an investigator from the Finnish Security and Intelligence Service (SUPO) also visited the scene. Suspicion of a bomb strike awoke when steel pellets were found in the wounds of the patients transferred to hospitals.