I would say its a Vigilante and not a SK because of the nature of the killing. SK seems like someone who will use knives or something more sinister. Blunt trauma force seems like a crime of passion pointing towards a Vig.
I would say the Vig targetted Rafay and the scum targetted Samus. Agreed with EM as well that i dont see why scum would take out a noob instead of one of the experienced players. So that points towards another noob as the scum who decided on targetting Samus.
I will take a look at Rafay's and Samus' day 1 postings later to see if there was anything they said that resulted in them being targetted,