Together with his uncle, Horvat led the uprising against Queen Mary and her mother and regent, Elizabeth of Bosnia.
He assisted King Charles III of Naples in deposing Mary and assuming the Hungarian crown in late 1385.
Elizabeth was strangled on the orders of Horvat's uncle, while Mary was eventually released by her husband, Sigismund of Luxembourg, who had recently been crowned king of Hungary.
Horvat's ally was Elizabeth's first cousin, King Tvrtko I of Bosnia, who appointed him and his brothers governors of Usora.
Sigismund and Mary then avenged her mother's death by having Horvat brutally executed in Pécs on 15 August 1394.