The story gives us no facts other than he shot and killed his wife and tried to kill himself. Who knows what type of suffering she was enduring. Maybe she asked him to take her life. I don't think if she did, that's his prerogative, but maybe it can help us understand if that was the case
A lot of unknowns are left unanswered.
Anyone who has endured serious long term pain and suffering easily gets despaired and a sense of hopelessness.
Surely, he did not have the supported and help he needed in taking care of her and himself. I have volunteered for many elderly people in my community who have no family interested in whether they suffer, live or die. It is quite terrible for them.