Someone posted a few days ago that the parents had the garage set up for sex orgies with locks from the inside so that the kids could not surprise them. And, that the mother had brought her friends back from the bar for her husband to enjoy. They then ordered pizza and retired to the garage, but not before checking to see that the kids' doors were closed. The alarm flashing didn't raise any suspicion because swingers always have people wandering in and out of their homes.
A few days before that, someone posted that the neighbor, who claimed to have danced with the mother, also claims to have heard of the swinging and had invited the mother to host one of the swinging parties at his home.
Oh, I forgot to mention that it was also posted from one of the swinger sites that the mother may have had sex in the parking lot of the bar that very same Friday night. I don't know how reliable this information is, but I have known some swingers, and it sounds about right. They only thing that they left out are the video cameras that the swingers inevitably use.
Anyone could have come in while the parents were partying in the garage and tried to join the party but settled for the child, instead.