The only way we can ever find out what really happened behind the doors of that home is if LE discovers a diary written by the Mom, Grandmother or Daughter, or did he show his true self in a former relationship (whoever they were, they were very, very fortunate Dr. Hyde didn't show himself to them). Perhaps hidden in the home or in a school locker, or a comment made to a friend, etc., one of them revealed who this man truly was. It's hard to believe he was so "wonderful" all of the time and then suddenly became this evil, demon possessed monster, and in such a short time. He'll NEVER tell the real reason, JMO, MOO.
From some of the articles, it sounds like he started with the mom (confrontation about something, break-up, get out, etc.), and he wasn't leaving any witnesses. We'll probably never understand the depth of depravity in a man like this. MOO