“I don’t know,” he said, shrugging. “Sometimes I pray for patience. Sometimes I just pray for a gun.”
I don’t need a gun; I have a Red Pen of Doom (DOOM, I tell you!), which I wield against all the idjits who think shrugged can describe how someone speaks. I could use more patience, though.
It would be all right (not alright, okay?) to use a comma after Sometimes at the beginning of each sentence, but it isn’t required.