Yaobang's death in April 1989 became the catalyst for the 1989 Tiananmen Square protests, during which people called for democratic reforms, an end to corruption, and the reinstitution of the "four freedoms". The protests were led by the Beijing Workers' Autonomous Federation (BWAF), a labour union independent from Communist Party control, and the Beijing Students' Autonomous Federation (BSAF), a self-governing student organization, which together called for the advancement of democracy and the end of dictatorship. After dialogue between the protestors and the government broke down, the government declared martial law and mobilized the People's Liberation Army to violently put down the demonstrations, resulting in the deaths of hundreds of protestors. In the aftermath of the protests, many of its leaders were imprisoned or went into exile, reforms were halted, a renewed political purge was undertaken and basic freedoms were further restricted. But it also resulted in the end of the second generation of Chinese leadership, with Deng Xiaoping handing power over to Jiang Zemin.