Carrying a pistol butt forward means the shooter intends to "cross draw". I.e. he's carrying the pistol on his LEFT side, but would reach across his body and shoot left handed. Most LEO's are not allowed u use a cross draw rig for liability reasons (takes longer to draw and presents an unprotected SIDE of the body to the "bad guy"), but detectives and "business cops" that often wear over the shoulder rigs often prefer a cross draw belt holster as well, since their normal rig would be cross draw.

If he WAS a cop, then he's pretty old school, because like I said, there's liability issues with wearing a cross draw rig, AND there's also liability issues with carrying revolvers.