I wouldn't really say he hid it. He openly displayed something. :P Just a matter of well it can be interpreted.

[@Vertigo]

You pick up a sense of loss. Though not for the kobolds. Hes fond of them, as hes gentle enough with the bodies but hes incredibly emotionally detatched from them. Its likely to do with the way hes looking at himself.

You could conclude he had been strongly reminded of his fragility. After seeing a group of kobolds that outnumbered the party get destroyed.