I agree. In my mind (this morning) Chris Senior made somebody really mad. I'm thinking he was having an affair and recently ended it. There are rumblings he may have been getting back together with Dana (rumor, but makes sense since he just bought her a new house and large piece of property). So let's say that hypothetically he breaks up with this other woman. She is livid. She has done so much for him. She decides she is going to take out everybody he cares about -- Dana, his kids, his best friend, his brother (but not the babies, because after all, she is not a total monster in her mind). She knows she can't accomplish this herself, so she convinces her brother or her best friend that she needs to do this to be able to go on. Maybe she offers to pay them. Somehow, she gets help. She kills everyone close to Chris, and then goes to his place last. "see this blood on my shirt? This is from your family. How dare you cross me? I have wiped every last trace of you off the earth. And now it's your turn." Bang x9.
This woman, by the way, that would have spent a lot of time at all of these properties and known where any security cameras were.
She may have also previously had been arrested for having severe anger issues.
Hypothetically, of course.