As Callum was born his parents brought him to an adoption center and became an orphan till then and he was moved to many places trying to search for a place to stay and that's why Callum doesn't have a specific accent and sometimes struggles to build up words in his mind. The place where he lived with other orphans was burnt down and many kids have died in there including the adults, some survived and this includes Callum, he sensed the fire was going down before it even started and decided to run away from the place, watching it burn down from a distance.
Callum was often called a psychopath due to his behavior and looks.
As he looked around town he saw a place where tattoos were made. At the age of 11 he got his first tattoo on his arm, being an amazing drawer and creative person he decided to become a tattoo artist so he became one at the age of only 13 years old.
He made awesome tattoos and at the age of 15 he was already filled with tattoos all over his shoulders, back and arms, this makes him very resistant to cuts and damage in general. As he kept being a tattoo artist he got kidnapped by a group of psychos, the scarred eyes was their name, they recruited Callum at the age of 17 giving him a big scar on his left eye and from then he started robberies and kidnappings, Callum was an expert of faking his psycho side and he looked totally normal to other people. Not until he goes out of his mind destroying the whole town with his group, most of his group was dead by then, some of them are unknown and he doesn't know anything about them.
Callum managed to not get caught and after weeks of running he took a plane to Chernarus. Wrong place at the wrong time.
Little note, this looks really bad and I will try to improve in those things later maybe with a little help, I've been working on this all day and I am exhausted physically and mentally.