Major Story arcs
The Old Gun was introduced in the series Grayson. It is explained that Christophe Tanner was victim of a school shooting in Geneva, the school that his two sons attended. The boys were both killed and Christophe lost the use of his eyes and had them removed. He then had surgery to connect his ocular nerves to his pistols, became part of the assassin community and took the name Old Gun.
Dick Grayson is tasked with capturing Old Gun after the gunman steals some enhanced eyes, ones that Spyral is looking for. Due to Grayson's hypnos being ineffective on Old Gun, he is accompanied by three other agents but the mission still fails. Later on, after asking Batman to research "Christophe Tanner", Grayson discovers Old Gun still has a son left and the boy has just started attending school. Dick is able to find Old Gun at the school and Tanner states that he took the eyes in a bid to connect himself to them but this process is not possible. Therefore, Tanner willingly hands over the eyes and even shares a joke with Grayson until he is shot by Alia, an agent of Spyral. Christophe retaliates and kills Alia before he dies of his wounds by his sons side.