Facing a serious threat to his government and possibly to his life, Assad for the first time lost his self-confidence and reacted with fury and desperation. His health also started to deteriorate during this period. Under his personal orders a campaign of repression was launched against the Muslim Brotherhood. Assad escaped an attempted assassination in a grenade attack in 1980. In response, troops led by his brother Rifaat took revenge by killing 250 inmates at Tadmor Prison in Palmyra. In February 1982, the rebellious city of Hama was bombed by Assad's troops, killing between 10,000 and 40,000 people. It was later described as "the single deadliest act by any Arab government against people in the modern Middle East." Over the next few years, thousands of Muslim Brotherhood followers were arrested and tortured, and many of them were killed or disappeared. Assad realized that his previous efforts to bring about national unity in Syria and to gain legitimacy from the Sunni urban population had totally failed. He was confronted with resistance from the Muslim Brotherhood and thousands of their followers. Large sections of the urban intelligentsia, professionals, intellectuals and former Ba'ath Party members, also regarded his government as illegitimate. Later, Assad used the threat of the Muslim Brotherhood to justify his heavy-handed rule.