Giannis Retzos was born in 1896 in the small mountainous village of Anogeio, Preveza, in the Epirus region of Greece. His early years were marked by hardship and unresolved tragedy. When he was just a teenager, his father disappeared under suspicious circumstances in 1909. It wasn’t until years later, while serving in the military in Ersekë in 1917, that Giannis discovered that his father's skeletal remains had been found in a hole, revealing that he had been murdered.

Driven by vengeance, Giannis contacted his younger brother Thymios Retzos, born in 1899. The two brothers tracked down and killed the men responsible for their father's death, igniting a criminal path that would span over a decade.

After committing the revenge killings, the Retzos brothers abandoned any pretense of living a lawful life. They disappeared into the rugged mountains of Epirus, forming a band of outlaws who terrorized the region through murder, robbery, and kidnapping. From the beginning, their crimes were ruthless and calculated. Together with their gang, they operated in hiding, targeting wealthy merchants and civilians, extorting ransoms, and silencing informants. Their ability to avoid capture made them infamous in local folklore.

Despite their violent actions, the brothers garnered a strange form of respect from some locals, perhaps due to the region’s long-standing history of banditry and resistance. But beneath this reputation was a reign of terror. Giannis, described as the ringleader, showed no hesitation in eliminating threats, including their own treasurer, Dimitris Bouzoukis, who was murdered for cooperating with police. They even killed their fellow gang members, Stavros Sintoris and Kontogiorgis, likely fearing betrayal.

In 1924, the Retzos brothers were unexpectedly granted amnesty by the Greek state. Their return to civilian life was strangely celebrated. When they arrived in the city of Ioannina, they were greeted with applause and hospitality. The security chief and local marshal even welcomed them personally, and the two settled into a lavish lifestyle in the city center. They lived in a two-story home near the gendarmerie headquarters and mingled freely with the city’s elite.

The most infamous crime committed by Giannis and Thymios Retzos occurred on June 13, 1926, in what became known as the Petra Robbery. That day, a National Bank vehicle was en route from Preveza to Ioannina carrying 15 million drachmas. The road had been blocked by a fallen tree which was an ambush set by the Retzos gang. As the vehicle slowed down, gunfire erupted from both sides of the road. The driver panicked, lost control of the car, and crashed. In the chaos that followed, eight people were killed.

The botched robbery shocked the nation. The brutality of the attack, combined with the high-profile target, triggered a massive response from the Greek authorities. Troops were dispatched, checkpoints were fortified, and the gendarmerie launched full-scale operations across Epirus and the surrounding regions. However, due to a series of bureaucratic blunders and slow coordination between regional law enforcement, the brothers managed to flee.

Their escape turned into an international manhunt. Giannis and Thymios first crossed into Albania, where they obtained new identities, Giannis as Athanasios Nikolas Tsikos and Thymios as Nikolas Petre Dissos. From there, they moved through Italy, Serbia, and eventually into Romania, where they were arrested briefly but managed to escape again. By the time they resurfaced in Varna, Bulgaria, they had assumed the roles of grain traders and operated an import-export business.

In late 1928, the Retzos brothers were finally tracked down in Bulgaria. Their capture was the result of close collaboration between Greek and Bulgarian authorities, as well as Romanian Security General Inspector Strati Stratilescu. They were extradited back to Greece in November 1928, ending their run.

Their trial began in September 1929 in Corfu. The brothers were charged for the Petra robbery and several murders. Sixteen individuals were tried alongside them. On October 7, 1929, the verdict was delivered: both Giannis and Thymios Retzos were sentenced to death, along with three accomplices—Evangelos Kokalis, Konstantinos Kapsalis, and Filippas Diamantis. The remaining accused were given life sentences.

The execution was carried out on March 5, 1930, under high secrecy and heavy guard. At 4 a.m., security forces arrived at the prison in Corfu. By 6 a.m., the brothers were transported under armed escort to the execution site near the old fortress. A crowd of junior officers and police cadets observed from a distance. The firing squad was composed of 30 officers, 15 soldiers, and 15 gendarmes.

At exactly 7:00 a.m., after a brief reading of the verdict, the command to fire was given. Giannis died instantly. Thymios, however, was still alive and visibly suffering. A final round of shots ensured the executions were complete. By 7:30 a.m., all five condemned men were pronounced dead and taken to a local cemetery.