Good morning.
First of all, I will go against my gut feeling and my experience and say that he may not be guilty. There is the idea that someone, (no ninjas here, trying to be serious) was sending them messages for 6-9 months, whenever it was. The rumor that Sheri was a big spender and if that was true and CC didn't make a lot of money at that job, then maybe they did want to remove Sheri's name off of everything to re-finance and get a better rate and save his credit from her bad credit. The contacted the cops because of the threats and because he stayed at home that monday night, decided to take it easy and clean out the basement of trash before summer started, for the kids. He unlocked the window and opened it, using it to get some fresh air. At night, he closed the window but forgot to lock it. Now, maybe, even though he was in the security business, he maybe forgot to set the alarm or maybe they didn't have an alarm thinking that the cameras was enough of a deterant, including the 6 LE who live in the area.
He had an arguement with his wife, all married men seem to do this at one time or another. We don't know how often or if this even really happened. He slept and woke up, leaving at 5:45 or so. Sheri and the boys should be waking up about then as the bus, if they take the bus, comes around 7 or 7:30. School starts around 8, also, so they woudl have been up and getting ready still. So, a killer got in through that unlocked back window, snuck in, killed them all, and wrote a message and left. CC called from the gym, with no answers he called the cops to check. He came back home, saw the bodies and freakout knowing that not only they were killed and gone forever but that the threat was true and he did have his family killed.
If the threats really did say, "keep doing this and your family will be dead." Then they would be prohetic in the final note of "I told you this would happen". So, the reality kicked in, he became histerical and rolled around on the lawn, flailing his arms. He is so crazy that it takes two officers to subdue him and they take him to the hospital in an abulance. (This is what happened, as neighbors saw him roll around and was subdued by the LE. I saw the abulance, with CC in it, still at the scene and then drive off, about 8:30.)