The unharmed girls tried knocking and no response. Called some guys to come break it down? Then when they arrived, called 911 saying unconscious because he wasn't responding, thinking he had alcohol poisoning?
Maybe so... The confusing part is that the roommates didn’t notice the evidence? The murders were so gruesome that the killer(s) had to have left a mess through the house.
Then again, maybe the friends came over before anyone noticed something was wrong?