I know the inside scoop on this. It's been years so I will remember it as best I can.
The shooter was
@York's hitman Gabriel, the assassination was entirely spur of the moment and was done in response to the harebrained scheme to execute a fake alaric
Because I knew York and knew he was planning to hit someone in the civil authority I didn't take an active part in the events but I did watch the speech that Knight's char Chancellor Glover gave in observer while Serpico was away somewhere else IC. I wasn't expecting it to happen when it happened. York had a pistol and that was it. The OTA and Proselytes locked down the apartment building within a minute of the shots and York died on the top floor
Immediately staff were trying to throw out the PK calling York's char a throwaway, York said he wasnt, and he wrote something in the rp docs to reinforce that impression
the truth is that the hitman char was essentially that, a hitman burner character, he only got used when someone needed whacked, so in one way he was a throwaway but in another it certainly wasn't the only person York had killed on that char. bluesuit assassins were the most useful tool