There were 6 bedrooms and 6 tenants not that long ago. Tenant No.6 moved out of the other second floor bedroom. Kaylee had moved out, but was visiting for the weekend. She was vacating the bedroom with the balcony on the third floor. It sounds like DM, one of the surviving tenants, was moving into the second floor bedroom, and was sleeping in that room on the night of the murders.
After checking on a noise for the third time from the second floor bedroom, he walked past her. She was frozen in fear, then she ran to the basement bedroom and locked the door. That's what I understood from the affidavit.
He didn't expect to get caught. He thought that: if he turned off his phone during the murders, no one would connect his phone to the murders. He didn't expect CCTV to connect his car to the crime scene because the car on CCTV had PA plates and no plate on the front, and five days after the murder he had WA plates.