Ömer Güni, a lieutenant commander who was fired from after the 2016 coup attempt, died of heart attack on Sunday, according to a Twitter account that claims to be a member of Turkey’s main opposition Republican People’s Party (CHP).

Lieutenant commander Güni was dismissed from the Turkish military with a decree issued by the Turkish government after the joup attempt on July 15, 2016. He faced several investigated over the past three years and accused of membership in the Gülen group, accused by the Turkish government of masterminding a coup attempt.

The group denies any involvement.