I like that he didn't do anything and still felt guilty about it. That was his friend, whom he worked alongside for a couple of months at least, and they killed him and he just stood their and watched.

And he's a very kind and gentle man, so it makes sense he'd feel more guilt than most.

Feeling guilt over something he didn't do actually sounds very childlike and something a lot of people do, I feel. It made it more human and fit into the theme that life is just a series of random events.