Backstory: Gideon Beaumont originally grew up in the Texas town of New Hope. New Hope was run by religious fanatics. These zealots had put in place a type of police force that would kill anyone that didn't share their beliefs and way of life, those who they deemed "fools." These police were called The Foolkillers, named after the original Foolkiller. As a boy, Gideon was presented with a challenge that he would have to complete if he wanted to become a Foolkiller and continue on his "righteous path." The task was to kill his own parents, who the town elders had judged as sinners and therefore fools, he completed this mission. One day the Mutant Gang of Outlaws known as The Lawless came into town and slaughtered everyone, leaving Gideon as the only surviving person. Gideon believed he had been spared by God and had been chosen to expunge the Earth of fools.
The death of Foolkiller 2099: In X-Men 2099 #33, La Lunatica uses "Psychic Touch" to make Gideon remember killing his parents, he was not able to handle this information and ended up blowing himself up.