The second death... a hulking figure with an armoured means Terminator armour, and the swinging wildly suggests a sword, or an axe, or something? Either way, you wouldn't swing with a lightning claw, yet a claw is present. The most likely suspect, in my opinion, is Abaddon the Despoiler. I know it's not much, but at least I've begun to narrow down the possible scum - as it's a twelve person game, perhaps we can begin to work stuff out.
Firstly, I imagine there's about three or four scum total - my money's on there being two Mafia members and a Tyranid.
Secondly, I'd imagine there's probably either one or two cops, one of which is dead. I can't think of anyone offhand for whom being a cop makes sense, unless the way it works is that Dark Angels are cops - which makes sense, given the way they act. I'm open to other suggestions, but if there is another cop I reckon it's Ezekiel.
Thirdly, there's probably one Doctor. No-one particularly logical springs to mind.
Fourthly, I'd be surprised if there wasn't a Vigilante - probably Commisar Yarrick, or perhaps a Blood Angel, but there are other possibilities.
Lastly, I'd expect maybe two more pro-town roles, for instance roleblocker (if I'm wrong about Ezekiel, perhaps a psyker as a roleblocker) or something unusual... I'll leave that up to the others to decide.
Oh, and I should mention: I'm highly up-to-date with Dark Angels lore, but I don't know that much about other armies. Just an FYI.
OK, we may as well get this started... Randomly