Why was Mohammad Reza Sharifi Nia imprisoned?

The memoirs of Ayatollah Hussein Ali Montazeri, published in 2000, offer the most credible account of the mass executions from a government perspective. Montazeri was, in 1988, one of the highest-ranking government officials in Iran, the designated successor of Ayatollah Khomeini as Supreme Leader, and the highest-ranking official known to have opposed the executions and to have sought to prevent them.