He sent the email about turning off the utilities a few days before he blew the house up, if I recall correctly.
If I am correct, I think that he was trying to divert his various supporters' attention from his true plans. If I had been his sister and had gotten an email outlining how to turn off the utilities, etc, I would assume that he was preparing against the eventuality of being arrested and held in jail.
Not too unreasonable under the conditions.
And that would also explain any new changes in mood or behaviour: he was getting stressed out about the possibility of arrest.
Give people an obvious explanation and they are less likely to think of a highly unlikely scenario: planning to kill his children and blow up the house. And so, less likely to take action in time to stop him.
He was obviously a planner and good at misdirection.