I have a question. What happened to Lou? He just disappears, did he just drop them off? Did somebody shoot or stab him outside? Was he somewhere getting something to eat? Was he just a driver and didn't want to get shot himself? He just vanishes.
He probably went off to whatever hangout the rest of Sollozzo's henchmen were at. He couldn't have gone in as it would have violated the conditions (the novel mentions that technically by him even being there as the driver it broke the terms of the meeting). So yeah, he dropped them off and went off to wherever, and as he was just some mook we don't know if he was killed in the war or whatnot.
