 CONT: When Tommy enters Reggios mansion he clearly gets shot in the  right shoulder/arm. His arm just hangs at his side and subsequently  he carries his gun in his left hand. When he reaches the basement  and finds his brother Vincent he is shown carrying the gun with his  right hand with his left arm being limp. In the same scene he  finishes clearing the room and has mobility in his left arm again to  grab Vincent. Then when he gets shot in the back he is back to  having a limp left arm and shoots the bodyguard with his right hand.