A high school teacher who has been kept in detention over alleged links to July 15 coup attempt for two weeks has been found dead at his prison cell in Istanbul.

Gokhan Acikkol was detained two weeks ago in Istanbul. Acikkol’s death sparked outrage while his father vowed to pursue legal charges against authorities over the tragic death. Speaking to media in front of Forensic Medical Council (ATK) in Istanbul on Friday, the father rejected any link to the coup attempt and said his son was denied access to his medics for the past six days.

An investigation into Acikkol’s death has been launched by authorities, the Cumhuriyet daily reported. The death comes amid reports of mistreatment and torture of thousands of people detained in aftermath of a botched coup on July 15.