Having been a successful assassin/bounty hunter he has been called in for more and more high risk contracts; one contract which was to kill an old fat business man that just had to disappear for awhile. As he was finishing his job and disposing of the man's body, he noticed a case in the businessman's office; a case under his office desk. Picking up the case hoping he was going to find something valuable he found a Atlas handgun with several clips for ammunition; his luck has finally smiled upon him he thought to himself as he took the handgun without thinking. With some cash in his pocket and a free top-notch quality handgun he made his way back home.
I hope that's a sufficient explanation.