From my understanding, the victims had all been asleep during the attack (several sources, including today's PC), but by the end, not all were killed in bed (see source below). I know some will suggest maybe E was sleeping on the couch or something, but I personally don't think that's what's being said here. I think whoever was killed first in the second floor bedroom, the other tried to flee and was killed on the floor of the bedroom or hall just outside the bedroom. If a downstairs roommate came up the stairs and stepped into the living room, that hall towards the bedroom would be right there in view. They would likely only see one body at that point. JMO.
Some of the murdered University of Idaho students were stabbed in their beds, coroner says
Of the four University of Idaho students who were found stabbed to death in a rental house last Sunday, some were killed in their beds, the Latah County coroner told CBS News Friday.
Coroner Cathy Mabbutt would not provide any further details. She noted, however, that earlier media reports stating all four victims had been murdered in their beds were not accurate