Not that I think this is a murder-suicide. But, if it was, couldn't it have happened that Bobby found the gun and took it to dispose of it or something? Maybe she wanted to protect someone, like her sister? It's bad enough to have 8 family members die, but, to have it splashed all over the news that someone in the family was the murderer could make it even worse? It might be better family reputation-wise to have the world think they were victims of a cartel, gang, etc?
Mind you, I think it would be unusual for a woman to be a mass shooter in this situation. It's pretty rare overall, but, you don't think about a woman murdering 7 family members, including her own kids and leaving her grandkids mother/fatherless. It could be another family member aside from Dana. I just figured IF Bobby would cover for anyone, it most likely would be her sister. But, realistically, depending how close the family was, she could cover for anyone of 8, no matter who it was.
I still don't think it was a murder-suicide. But, I could see with the single-wound person that it could be. So, maybe that's why the police came looking for her in the middle of the night?