>>280480684
No he obviously cared about Grenn he reminisces about him when he hears the music box go off and thinks he's about to die.

And he smiles because he thinks Grenn has become suspicious and misanthropic like him to suspect the gift, he's all about racing to the bottom and unapologetically being the worst you can be, he smiled because he thought for a moment maybe Grenn was as bad as he was.

Consider this line, he continues talking to himself after the shootout with Grenn.