Genuinely distraught over Peter "Parker" Yang. This rough-n-tumble guy who, while physically intimidating, has a heart of gold. A working P.I. who was on a case and just happened to stumble into this drunkard in Jack's Bar, who seemed morose, who seemed like they needed help. And Parker helped him, easing him out of his shell, became his friend, and worked with him. He pulled Arthur Lester out of his self-hatred to help people, and in doing so, helped Arthur Lester himself.
He loved the guy. Brought him to his parents' house. ("They love you!") He's two thousand dollars deep in gambling debt and still bought his friend a piano because he knows he used to play. This man who sounds like he's inhaled more cigarette smoke than air wants Arthur to date his sister because it means they could be brothers. This man who tells Arthur that he's the brains of the operation, that once told him he was at bedrock, tells him to lighten up and not let the past drag him down. This man who knows Arthur doesn't like to be coddled, so he tells him what he needs to hear, but doesn't push too much.
This man who turned on the kettle to make tea for the two of them (how often did they do it? How often did they joke and laugh and start the day with a cup of tea before their first client?), who rushes to Arthur when he starts to shout, whose last words were, "Artie, breathe," who died trying to help his friend.
Parker Yang died from senseless violence from a being that did not yet have any humility or understanding of how precious life was, and Arthur followed him only a few seconds later.