That's pretty much the way I see it as well. Or something similar. I'm going to speculate Reis was hooking up with Saturley back at the bar (in the presence of her previous boyfriend) and decided to bring him back to her brother's and Reeves' place to continue the fun. At first Reeves likely thought he'd be cool with this but as the night wore on and fueled by jealousy, humiliation, stress and alcohol, Reeves finally lost it when they got home.
Why others here are intent on pursuing a homosexual angle to this story is beyond me.
Spot on.