During the 1st few viewings of 'the Dusk', I always had assumed Richie had killed hostage Gloria just because he was so inclined to do so.
His explanation to Seth about how 'she became a completely different person' when Seth left the room seemed like a lame excuse, for what looked like the needless slaughter of someone, who could have been your friend's mother.
However, after watching 'the Dusk' over & over, I noticed something new recently:
When Richie is alone in the motel room with Gloria, she looks at Richie's gaping, blood-soaked, mess of a hand.
And then some creepy sounds come over, similar to the sounds used later on in the Titty Twister, when the vamps start seeing blood and turning nasty.
As the viewer never gets to see the struggle between Richie & Gloria; could it possible Gloria might have been a vamp, and that she really 'became a completely different person' when Seth left to get the burgers? ???