My guess is that he was not working for Welcome Wagon
Yep. He was carrying to protect himself from his "friends" with whom he was still running. He knew he was going back to the graybar hotel, not just the county clink, if the cop found his gun, even though this was just a traffic stop.
Seeing the gun, the cop knew that failing his self-preservation instinct, someone else would be collecting his pension.
Quad Erat Demonstratum.