As a child, O'Donnell was tricked by his parents, who abandoned him on the steps of a church, forcing him to take care of himself from then on. Ever since, he felt embittered, taking his frustrations out on churches throughout London. While O'Donnell was known to destroy confessionals and throw explosives at tabernacles, the Metropolitan Police Service never managed to apprehend him.
After he stole an organ pipe, Sergeant Frederick Abberline contacted his Assassin allies, Jacob and Evie Frye, requesting they brought him in alive. The twins did as requested, abducting O'Donnell near one of London's many churches, and delivering him to the authorities.