This may be true, that he had some personal motive and rage we don't know about, but MS also clearly knew it was gonna happen. His phone call to Dr. P., a man he was not emotionally connected to at all, the night before proves that. He might as well have said, "Hey, Dr. P.! It's me, Mark, Teresa Sievers's husband. Look, I'm gonna need you to be part of my alibi tomorrow when you find my wife's dead body. So this is me, calling you, leaving you a voice mail to let you know only Teresa is headed home to Florida tonight. The kids and I are staying in Connecticut for a few more days. So, when you get to the house tomorrow, don't worry that the kids are there, either! They are safe with me. Just tell the cops I'm out of town so it can't possibly be me? K? K, bye."