He had a ringside seat for the entire, bloody rise of ISIS, and by his own count killed dozens of innocent men, women and children. Now facing likely execution, Thahir Sahab Jamel disavows the black-clad Islamist army, but his Kurdish jailers say they’ve heard it all before.

In a jailhouse interview with FoxNews.com in the Kurdish-held city of Kirkuk, Jamel, 27, detailed how he joined Islamic State in 2013, served as a foot soldier in the takeover of Mosul a year later and, he claims, eventually became disillusioned with the dark vision of his fellow fighters.

“At the beginning, ISIS told us we would all go to heaven,” Jamel said, speaking under the watchful eyes of Kirkuk police guards. “But now that I am in prison it means I am going to the fire. I am going to hell.”

Handcuffed and partially masked, Jamel, who has been in solitary confinement since his arrest two and a half months ago, said he joined the terror group like many other young Sunni Muslim men opposed to the Shia-led government in Baghdad.