Trobec was born on July 6, 1948 and lived at a farmhouse near Ljubljana, in what was then Yugoslavia. He worked as a driver. Slovenian reporting called him the Monster of Gorenje Vasi, after the hamlet.
In 1978 he brought six people to the house, raped and strangled them, and burned the bodies in the bread oven in the yard. The dead were Vido Markovic, eighteen; Marjan Cankar, fifty-two; Urska Brecko, twenty; Ana Plevnik, forty-two; Zorka Nikolic, thirty-five; and Olga Pajic. All six died in a single year.
He was arrested and tried, and sentenced to death in 1980. Yugoslavia carried out few executions in this period and the sentence was commuted to twenty years, which was the maximum determinate term available. He served it and was released.
He hanged himself on May 30, 2006.
He is the best-known Slovenian criminal case of the twentieth century, and the destruction of the bodies in the oven is what the case is remembered for; it also meant that the physical evidence at trial was largely ash and fragments. The accessible sourcing is Slovenian-language material.