Complex sentence: Two years later, he was killed by mafia in Palermo: initially suggested to be an act of terrorism, his assassination was probably spurred by its strong commitment against the relationships of numerous Sicilian politicians (mostly members of DC itself) with the Mafia.
Split into simpler sentences: Two years later, he was killed by mafia in Palermo. Initially believed to be an act of terrorism, his assassination was probably spurred by its strong commitment against the relationships of numerous Sicilian politicians (mostly members of DC itself) with the Mafia.