Buy a Bullet

Buy a Bullet is a 2016 thriller short story written by Gregg Hurwitz. It forms a part of the "Orphan X Thrillers" series by the author. Being a short story it was published as an electronic book.
The follow-up books in the series are "The Nowhere Man" (Released in January 2017) and "Hellbent" (released in January 2018).