But wasn´t that exactly the case with Sheila? She had never lived independently of her parents. She depended on money, flat, food, medical bills - everything from them, probably also emotional support and let´s not forget, the control that comes with all of that. Colin too while they were married. Car, flat and on and on. Never independent.
She lived in her own place she wasn't subject to their roof. They were not her guardians at that point. When subject to the roof of someone else and thus their rules and they won't let you do something that is when children kill their parents. They don't plan to commit suicide though in such paradigm it is to kill their parents so they can be free and then go do what they want to do. It is not part of murder suicide. In fact if we look at such it applies to Jeremy.
Jeremy was more trapped than Sheila. She was living away from them. He was the one who had them provide his car, place to live etc and even the ones who provided him with the murder weapon. They would not let him have his first choice of a semi-auto shotgun though. He had to work for things while Sheila didn't so he was jealous. He wanted to live free of their control and just have all their money at his disposal. He didn't want to share the wealth so killed everyone. If the goal is not money and just raging against authority that paradigm features killing people until police manage to arrest or kill them. It's not suicide at their own hands.
Killing dependents as opposed to authority figures is often a feature of murder suicide. The main reason for this is because knowing the dependent is alive is a mental obstacle to committing suicide.
Then feel an obligation to keep taking care of the loved one. If the loved one can take care of himself or herself and is not dependent then there is no obstacle but when dependent there is that obstacle. If a parent is dependent upon you to survive it provides as much a reason to live as having a child that counts on you. Another is they rationalize the dependent will suffer emotionally from their loss. Children of suicide victims need counseling and have severe problems. Killing the dependent eliminates having to feel guilty that killing yourself will cause such problems. Even jealousy can play a role. They don't want a spouse to end up with a new husband/wife or their kids a new father/mother.
So the murder suicide paradigm features killing people whose existence deters you from killing yourself.
The revolting against authority takes different forms:
1) hoping to get away with murder
2) going on a rampage until stopped by being arrested or jailed
3) going on a rampage and once trapped and knowing you will be going to jail killing yourself to avoid it. Often this will involve suicide by cop but plenty do take their own lives as well.