The arrival of Andronikos Komnenos was soon followed by a massacre of the city's Latin inhabitants, who virtually controlled its economy, resulting in the deaths of thousands of Westerners. 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 Andronikos had the Empress Maria imprisoned and then killed – forcing a signature from the child Emperor Alexios to put his mother to death – by Pterygeonites and the "hetaireiarches" Constantine Tripsychos. Alexios II was compelled to acknowledge Andronikos as colleague in the empire in front of the crowd on the terrace of the Church of Christ of the Chalkè and was then quickly put to death in turn; the killing was carried out by Tripsychos, Theodore Dadibrenos, and Stephen Hagiochristophorites.