Weidmann was born in 1908 in Frankfurt and had served prison terms in Germany for robbery. He came to France in 1937 and, with two accomplices, Roger Million and Jean Blanc, ran a scheme of kidnapping people for ransom that turned immediately into killing them.
Between July and November 1937 he killed six people: Jean de Koven, a twenty-two-year-old American dance student he lured to a villa at La Celle-Saint-Cloud and strangled; Joseph Couffy, a chauffeur, shot for his car; Janine Keller, a private nurse, shot in a cave in the forest of Fontainebleau; Roger LeBlond, a theatrical producer; Fritz Frommer, a former acquaintance; and Raymond Lesobre, an estate agent shot while showing him a property.
He was arrested on December 8, 1937 at the villa, after a business card left with one victim's family led police there; he was overpowered after wounding an officer.
He was tried at Versailles in March 1939 and sentenced to death. He was guillotined outside the prison Saint-Pierre at Versailles on the morning of June 17, 1939.
That execution is why the case is remembered. The crowd was large, unruly and drunk, spectators soaked handkerchiefs in the blood as souvenirs, and photographs and film taken from windows overlooking the scene were published. The government of Edouard Daladier abolished public executions by decree within days; every subsequent execution in France took place inside a prison. Christopher Lee, then a teenager, was among the spectators and wrote about it decades later.