William II of Sicily
There were several revolts, leading to an invasion by King William II of Sicily. On September 11, 1185, during his absence from the capital, Stephen Hagiochristophorites moved to arrest Isaac Angelos, whose loyalty was suspect. Isaac killed Hagiochristophorites and took refuge in the church of Hagia Sophia. He appealed to the populace, and a tumult arose which spread rapidly over the whole city.