German police have arrested an armed 31-year-old man who boasted during a sting operation that he had supplied the Glock 17 pistol used by a teenager who killed nine people in Munich on 22 July, the Frankfurt state prosecutor said in a statement. Authorities arrested the man, who was not named, in Marburg, about 65 miles (100km) north of Frankfurt, after contacting him on the so-called darknet and posing as buyers for an automatic weapon and another Glock 17 pistol for €8,000 (£6,920), it said. The man’s claims were apparently supported by evidence gathered by the Munich prosecutor’s office and Bavarian state police. “There is the strong suspicion that the 31-year-old man sold the Glock 17 used in the Munich shooting to the 18-year-old German-Iranian shortly before the attacks,” the Bavarian state police said in a separate statement. The Frankfurt prosecutor’s office said the suspect was identified during unrelated investigations into illegal weapons purchases by a 62-year-old accountant from the state of North Rhine-Westphalia and a 17-year-old student from the state of Hesse. Facebook Twitter Pinterest Memorial for the victims in Munich. Photograph: Johannes Simon/Getty ImagesDuring the course of a subsequent sting operation, the suspect said he had sold the pistol during a meeting in Marburg on 20 May, followed by 350 rounds of ammunition during a second meeting on 18 July, according to the statement. The gunman went on to kill nine people in Munich, then shoot himself. Evidence gathered from the gunman’s home and various social media messages indicated that he had taken a bus to Marburg from his home in Munich in May to buy the weapon, and again in July to buy the ammunition, the Bavarian police statement said. It said a 65-person task force investigating the Munich shooting was continuing to review 3,100 tips and pieces of evidence, and had already interviewed 250 witnesses. To date, there was no new evidence indicating that any other parties were involved in planning or executing the shooting, the Bavarian police said. “The successful investigation proves once again that there is no complete anonymity on the internet and no comprehensive protection against prosecution,” the Frankfurt prosecutor’s office said. “This is also true for the so-called ‘dark net’.” Alexander Badle, a spokesman for the prosecutor’s office, said the 17-year-old student was a German citizen and there was no evidence that he was planning a Munich-style shooting attack, despite the “quite concerning” amount of weapons he had amassed. Nor was there any evidence thus far of any specific political, religious or ideological motivation for his actions, Badle said. He said the youth was facing charges for violating Germany’s strict weapons laws, but had been released for now.The 62-year-old acccountant had also been released.