Reluctant to participate at first, Keene ultimately agreed after his father had a stroke, motivated by the idea of getting to spend time with him. "Black Bird" is based on the 2010 autobiographical book "In with the Devil: a Fallen Hero, a Serial Killer, and a Dangerous Bargain for Redemption" by James Keene and Hillel Levin, which recounts Keene's real-life experiences from that mission.