Luigi Chiatti was born Antonio Rossi on 27 February 1968 in Narni, a town in the province of Terni, central Italy. His biological mother, Marisa Rossi, was a young maid who was unable to support him and abandoned him shortly after birth. The infant was placed in a local orphanage near Narni, where he spent the first six years of his life.

On 13 June 1975, Antonio was officially adopted by Dr. Ermanno Chiatti, a respected physician from Foligno, and his partner Giacoma Ponti. Upon adoption, his name was changed to Luigi Chiatti. He grew up in the provincial town of Foligno and was considered intelligent and academically capable, eventually studying architecture. However, he struggled with emotional and psychological instability throughout his adolescence and early adulthood. Reports from his later trial would describe him as socially isolated and potentially traumatized by early childhood experiences, including allegations that he had been sexually abused by a priest while in the orphanage—claims supported by testimony from a childhood acquaintance during his defense.

On the afternoon of 4 October 1992, four-year-old Simone Allegretti disappeared in the countryside between Foligno and Bevagna. His body was discovered two days later along an escarpment, close to the area where he went missing. Just before the discovery, a note was found in a telephone booth at the railway station in Foligno. This note claimed responsibility for the murder and provided details about the location of the body and the clothing that Simone was wearing. It also indicated that the murderer was willing to kill again.

In response, the police in Perugia set up a toll-free number and issued a note to the killer. On 13 October, a man identifying himself as the "Monster of Foligno" called the toll-free number multiple times. This led the police to investigate Stefano Spilotros, a Lombard real estate agent. However, inconsistencies in his alibi and testimonies from his friends and relatives excluded him from being guilty. The intense public panic surrounding the case led to other tragic events, including the suicide of a young worker from Macerata, who claimed he was the monster in a note he left behind.

On 7 August 1993, Chiatti struck again, killing 13-year-old Lorenzo Paolucci. Lorenzo’s body was found just 30 feet from Chiatti's villa. The police followed the evidence to Luigi Chiatti, and he was captured. Chiatti confessed to both murders within a short time.

On 1 December 1994, the trial against Chiatti started for the murders of Simone Allegretti and Lorenzo Paolucci. On 28 December, he was sentenced to two life sentences.

However, on 11 April 1996, the Court of Appeal of Perugia changed his sentence, declaring him semi-mentally ill and reducing his punishment to 30 years of imprisonment. This decision was upheld by the Supreme Court of Cassation on 4 March 1997. During the court proceedings, a witness from an orphanage testified that both he and Chiatti had been sexually abused by a priest.

Chiatti served his sentence in the prison of Prato, Tuscany. He asked for early release twice, but these requests were denied. In June 2009, there were rumors that he had been released from prison for a few hours, but his lawyers denied this.

On 3 September 2015, Chiatti completed his prison sentence but was required to stay for at least another three years in a Rems facility in Capoterra, Sardinia. His stay there was extended twice by the Surveillance Court of Cagliari, in 2018 and 2020, after evaluations indicated he remained a danger to society.