(WILL MAKE MORE DETAILED)
Leon mars was born in Beaumont, Texas to a drug addicted mother in a crack den. She dropped him off at a fire department with only a single Notecard - "Leon." The fire chief, a man by the name of Alexander Mars, decided to adopt the kid. He raised him tough and as soon as he could shoot a gun and hunt, He did. He was almost raised by the Texas Light Foot Militia and was steeped in Militia and Anti-government culture since before he could remember. This raised him to be tough and gave him skills he would need to survive any catastrophes.
He decided to take a trip out east in order to learn more about Russian firearms and tactics and unfortunately got stuck in Chernarus during the mess that is the apocalypse.