Something about that time line seems off.
If the guy on the call did it, he had to have been very close to the murder scene on that last call. Did he live close by or was he parked outside or already on his way? Maybe that's why he wasn't named a suspect? If he was on the phone at 2:52 but GPS information on the phone shows him not near the site, he has an alibi.
Was it reported that the victims were likely asleep at the time of the attack. If so, Kaylee fell asleep in a hurry.
I made up the time of crime.😶