One detail I have not heard discussed here is that the surviving sister said the father's Glock was silver yet the police say the shooter staged a black Glock on the 13 year old brother. And police knew something was up because it HAD NOT BEEN FIRED!
Sources close to the investigation told DailyMail.com that they believe the teen had been part of what appears to be a murder-suicide plot with his 13-year-old brother who died in the bloodbath.
www.dailymail.co.uk
Now, the color of the gun is not significant but in order for the staged gun not to have been fired there would have had to have been 2 guns in the house. That leads to other potential scenarios.