Manuel's death on 24 September 1180, marked a turning point in the fortunes of the Byzantine Empire. When Manuel died, he was succeeded by his young son Alexios II Komnenos, who was under the guardianship of the empress Maria. Her conduct excited popular indignation, and the consequent disorders, amounting almost to civil war, gave an opportunity to the ambition of Manuel's estranged cousin, Andronikos I Komnenos (r. 1183–1185), son of Isaac Komnenos. Andronikos left his retirement in 1182, and marched on Constantinople with an army that (according to non-Byzantine sources) included Muslim contingents. His arrival was soon followed by a massacre of the Latin inhabitants, which was focused on the Venetian merchants who were settled in some numbers in Constantinople. He was believed to have arranged the poisoning of Alexios II's elder sister Maria the Porphyrogenita and her husband Renier of Montferrat, although Maria herself had encouraged him to intervene. The poisoner was said to be the eunuch Pterygeonites. Soon afterwards he had the empress Maria imprisoned and then killed, by Pterygeonites and the "hetaireiarches" Constantine Tripsychos. Alexios II was compelled to acknowledge Andronikos as colleague in the empire, but was then put to death; the killing was carried out by Tripsychos, Theodore Dadibrenos and Stephen Hagiochristophorites. Andronikos, by 1183 sole emperor, married Agnes of France, a child twelve years of age who had been formerly betrothed to Alexios II. Agnes was a daughter of King Louis VII of France and his third wife Adèle of Champagne. By November 1183, Andronikos associated his younger legitimate son John Komnenos on the throne.