We don't exactly even know how many cars away he was from the one where most of the fighting happened. On a train, especially an old-fashioned one, I doubt you hear handguns a couple of cars away at all. Why he wasn't with the others, is another question of course. Still, in the previous eps we often saw him alone, in his library or otherwise, and not really partying with his men, so in that sense it's nothing special. But all in all I hadn't got the kind of impression he would willingly let all those people die just to teach Chiko a lesson on the hardness of life... I'm inclined to think he found out too late.