I've gotta say, It's crossed my mind and I don't think anyone has mentioned this yet, but for all we know this isn't the first time for Craig. He's a pretty volatile person. Maybe this time he just got sloppy. Who knows.
But like Shawn said, God help Craig and Kelly... and my condolences go out to Melissa's family, whatever kind of person she may have been, she did not deserve to die like that.