A suicide like this has happened before. It even involved the fuel being shut off.
hanlon's razor and all that
The fuel switches have been very carefully designed to take "stupidity" out of the equation.
It's going to be hard to conclude for sure that this was suicide without some form of note or other evidence we don't have yet, but really, at some point the effort it takes to come up with alternatives is going to start looking silly.
Or someone was lying.