Most of his neighbors did not know Mustafa Karahan’s past. When a 63-years-old man’s body was found among the ruins of his apartment last Sunday, along with an elderly man and his granddaughter, it was first thought that the explosion that devastated the place was the result of a natural gas leak. But further investigations disclosed a potential plot for revenge, orchestrated by Karahan, and the elderly man’s dark history, including involvement in murders and a far-left group.

Karahan was in his second-floor apartment in a three-story building in Fikirtepe, an old neighborhood in Istanbul’s Kadıköy district, which was going through what is called "urban transformation," an urban renewal project. His was among the few buildings that people did not leave to make way for demolition. The "demolition," ironically, came in the form of a powerful blast, which only an Uzbek national managed to escape. That man was the son of the second victim of the explosion and the father of the 10-year-old girl. The survivor was apparently working as an assistant for Karahan.

On Wednesday, Turkish media outlets reported that Karahan – who was identified as someone with ties to far-left groups in the past earlier by the Interior Ministry – was wanted by Swiss authorities over the 1998 murders of four people in a restaurant. Known as "Safari Murders" after the restaurant they took place, the incident ended up in the deaths of three Turkish staff and a patron. Karahan’s blood stains were found at the scene and authorities issued an arrest warrant for him. Karahan had apparently illegally entered Switzerland in 1989 after leaving Türkiye where he was imprisoned in a case regarding a far-left group. Swiss security forces raided his home but he had already left the country. Years later, they discovered Karahan had fled to Türkiye and in 2008, an international arrest warrant was issued for Karahan. In 2011, Switzerland asked Türkiye for his arrest and extradition. One year later, he was captured, thanks to a tip-off by his older brother and arrested. Yet, an Istanbul court rejected his extradition and Swiss claims that the attack was an act of terrorism and instead, sentenced him to life in prison. Karahan was released in 2019 on parole and settled in Fikirtepe, where he worked as a plumber.

An investigation following the explosion showed that Karahan was harboring hatred toward his brother and other family members for their help in his capture and was not mentally stable. A.K., the only survivor of the blast, was working with him and staying in the same building with his family. The investigation showed that Karahan was collecting gunpowder he extracted from fireworks he bought and once told A.K. that he would make a pipe bomb and "blow up his brother." He was trying to remove the gunpowder from a piece of firework shortly before the explosion. The powerful explosion tore down his apartment and an ensuing fire spread to nearby buildings before firefighters extinguished the flames.