Background
He's a dropout slicer from the imperial academy. On a dare amongst his classmates he hacked one of his instructors terminals. He learned how the Academy would manipulate test results, even sabotage their projects to pit the students against each other. Growing frustrated from the hypocrisy and corruption of the instructors at the Academy, they were no better than the Governor of his home world who expropriated his parents business just to enrich himself. So he used his Slicing skills to fake his death. They only one who knows he is still alive is his former best friend. She caught him sneaking on to a shuttle, but let him go. She's still believed that the empire was bringing order to a disordered galaxy. Her turning a blind eye to his AWOL was a one time thing, and if she ever saw him again she would arrest him herself.
knowing he could never go home again he traveled from one backwater planet to the next taking any odd job that came his way. Eventually he started taking jobs from a guy named Wedge. Who slowly recruited him to the rebels after showing him the good they were doing to support the people that they empire had forgotten
Motivation