I'm sure that everyone has their own theory on what went on that night. This is mine.
Dad hears someone trying to break in - either he hasn't been home from work for long or he was a light sleeper. He opens the door to confront whoever is breaking in and he gets shot - maybe killing him, maybe not. Mom was probably in bed asleep because she had to go to work in the morning and get Jayme off to school. Maybe Dad yells something as he opens the door or the shot itself wakes her. She comes out and sees her husband laying on the floor shot, maybe still alive, maybe struggling with whoever it is breaking in. She flips out and joins the attack.
Because to be honest - from experience - the first inclination is not necessarily to hide or be fearful but to be angry that someone is trying to invade your home, your privacy, harm your family. Jayme probably wakes up hearing the commotion, maybe she hides in a closet, or tries locking her bedroom door. Maybe she turns on her cell phone, maybe not. Maybe she comes out of her room to help her parents, her father is probably dead at that point, maybe Mom is on the floor close to death, the intruder grabs Jayme and starts dragging her out, she is struggling and maybe yelling help and no! Maybe yelling for her parents. Maybe mom or dad is still alive enough to turn on a phone but are unable to speak. Or Jayme has her phone and already had it on when she came out of the bedroom. I'm sure that between 12:30 and 1:00 there was absolute crazy chaos in that house.
It does remind me so much of what happened with little Shasta and Dylan Groene and Joseph Duncan. He managed to kill their parents and teenage brother with just a hammer, if I remember correctly. People like this aren't sane. They don't often think like regular people so what seems logical or easiest or sanest doesn't apply. I see many people saying things like "Why didn't he just do this or that? It would make more sense."
Because people like this are insane, nothing they do makes sense. They know what they want and they don't care how they go about getting it.
JMHO