Aung Gyi, a senior army officer who served briefly in Myanmar's post-coup military junta but later became a founder of the country's pro-democracy movement, died Thursday at age 93.

His family says he died from cardiac arrest.

Brig. Gen. Aung Gyi was army number No. 2 and then also served in the second position in the junta set up after commanding Gen. Ne Win seized power in a 1962 coup. However, his public comments about the coup and economic policies caused his ouster in 1963.

He was imprisoned in the 1960s, 1970s and 1980s for his continuing criticism. But his open letters to Ne Win about economic reform were a catalyst for the discontent that led to the failed 1988 mass pro-democracy uprising that toppled his former superior.

He became chairman of the National League for Democracy party which he joined Aung San Suu Kyi in founding at the height of the 1988 unrest. However, he resigned shortly afterward, alleging communist influence in the party. He founded his own party, but it won just a single seat in the abortive 1990 election.

Despite a conciliatory nature, he found himself at odds with many in Myanmar's pro-democracy movement because of his never-discarded personal loyalty to Ne Win and the army as an institution.

He is survived by his wife and four adult children.