Arthur Gatter (1940 – December 12, 1990), nicknamed The Hammer-Killer of Frankfurt, was a German serial killer who killed six homeless people and two homosexuals in the city parks in 1990. Murders The murders occurred from February 1 to May 22, 1990, in the outskirts of Frankfurt. Frankfurt at the time had around 2,400 homeless staying in the city and especially in the greener areas. February 2, 1990: a crime scene was found in Weißfrauenstraße. A security guard found the homeless 43-year-old Hans-Peter "Peterchen" S. at 5:00 AM. February 7, 1990: Another victim, 22-year-old Kurt Helmut H. was found with fatal head injuries. He was not a homeless person, therefore initially no connection to the first victim was established. April 2, 1990: At the bus stop at Rechneigrabenstraße. At 5:40, the tramp Helmut R. was found with severe head injuries which lead to his violent death. April 3, 1990: Two victims were killed near the Eschenheimer plant. The police reached to this and founded the special operation "Berber" under Commissioner Karlheinz Wagner, and measures were taken. For example, dolls were draped as potential victims on park benches and plainclothed officers were to lure the offender as "decoys". April 9, 1990: Helmut R. was murdered in Ostzeil. April 11, 1990: A homeless man said he saw a man approach a sleeping person with a blunt object. After a facial composite was made, a suspect was arrested in Gallus, but had to be released due to lack of evidence. May 4, 1990: 46-year-old Hans-Peter M.'s bloody corpse was found around 7:30. May 5, 1990: 60-year-old Engelbert G. and 42-year-old Nicola Z. died about 50 meters apart. A crime scene photo with a bloodstained park bench visualised the brutality of the act. This meant that three homeless people had been murdered within 24 hours. The police tried with surveillance technology (including stealth cameras in bird houses) to catch the culprit red-handed. However, the diffused parking lights and the inadequate camera technology were not enough to attract investigation-relevant images. Even a survey of dry-cleaning companies on whether blood-stained clothing has been delivered, provided no results. In the homeless scene, the fear was reversed and the city put up additional shelters and left the subway stops open overnight, so that as few people as possible had to sleep on park benches. May 20, 1990: Brazilian native Anderson S. followed a man into a bush, supposedly