Claude Lastennet was born on January 19, 1971, in Brest, France. He came into the world just a few minutes after his older brother, Frédéric. Their father was a sailor who did not have much interaction with the family. As a result, Claude and Frédéric were raised separately by their aunts and uncles in Crozon. Meanwhile, their mother, Jacqueline, moved to Paris for work as a postal worker.

Two years after they were born, their mother brought them to live with her in Paris. However, in 1983, the family moved back to their original area in Morlaix. In 1984, Jacqueline married a man who was ten years younger than she was. This marriage caused Claude to feel betrayed since he was very close to his mother. The relationship between Claude and his stepfather was strained, mainly because his stepfather struggled with alcoholism. This conflict pushed Claude to leave home when he was just 14 years old in 1985.

After leaving home, Claude focused on his education. He graduated from a school in Quimper with certificates in restaurant management and pastry-making. He later worked as a seasonal waiter at a hostel. By around 1987, he began using hashish and even started dealing drugs at the hostel where he worked.

In 1990, Claude was discharged from the French Army. He experienced a mental breakdown when he learned about his grandmother’s death. Following this, he voluntarily admitted himself to a psychiatric hospital. The next year, he got a job at a restaurant in Montparnasse called Chez Dumonet. While there, he gained a reputation for having relationships with older female customers. His refusal to serve customers he disliked eventually led to his dismissal from the restaurant.

In February 1993, while staying with his brother in Paris, Claude attempted suicide by swallowing a medication called Lexomil, but he survived. Several months later, he stopped taking his medication and began searching for elderly people on the streets.

On August 24, 1993, Claude Lastennet committed his first murder. He broke into the home of 87-year-old Marcelle Cavilier in Chevilly-Larue. After threatening her for money, he strangled her when she refused. He stole 12,000 francs from her home before leaving. When her family arrived later that day, they found her dead.

On November 15, 1993, Lastennet attacked 76-year-old Antoinette Bonin in Thiais. He broke a window to enter her home and strangled her. Her son, François, found him there. Lastennet claimed Antoinette had an accident. After he fled, François called the police, who initially suspected him.

The next day, on November 16, Lastennet murdered 72-year-old Raymonde Dolisy in Boulogne-Billancourt. He strangled her and robbed her home. Her body was discovered three days later.

On December 18, 1993, Lastennet killed 91-year-old Augustine Royer in Bourg-la-Reine, strangling her to death. Her body was found the next day. Investigators linked these murders to the same route in their investigations.

On January 8, 1994, Lastennet broke into the apartment of 92-year-old Violette de Ferluc in Thiais. He strangled her and stole from her home. Her son found her body the next day.

Lastennet was arrested on January 12, 1994, after a friend alerted the police about a credit card he stole from an elderly woman. Following his arrest, he confessed to all the murders and explained his choice of victims. In October 1997, he was convicted and sentenced to life in prison. He died on December 19, 2023, while serving his sentence.