I think that priest is the bad one and the guy is the good one, so, the priest tried to kill Shanoa but the gun guy stopped him.
Or it could be the complete opposite: Barlowe? (The priest) could have been trying to give Shanoa the power or Glyph she needed to defeat Dracula, Albus (the gunslinger) could have hurt Shanoa off frame (hence why she's on the floor) and Barlowe was simply trying to protect himself and her while Albus tried attacking him.
Or as you stated, Barlowe could have attacked her and Albus showed up in time to try and defend her. (The fact that what looks like Dracula's coffin being behind them does seem to support that.)
But from the way it is in the video, I think it's the former: that Albus attacked to get the glyph and Barlowe was defending himself.
Maybe the scene before, where she was suppose to be getting three of them, would have merged into one glyph, thus creating the weapon needed to defeat Dracula and that's the scene right before the attack.
Also, back to the coffin: I got the impression that Dracula was already awake and causing serious problems with his minions before the Order even formed or at least, shortly after. So what's he doing possibly asleep, ready to be resurrected? And why is his coffin seemingly, at the Order's base? (The background looks like a church/temple thing and I figured that's where the order would be stationed.)
And will we get to meet/talk to him in the game, pre final boss fight? Cause I got this pic:
I'm not sure who it is but...::hunches::