Being psychotic doesn't necessarily mean being angry. I think you need to have it clear in your own mind whether you think she did it in a fit of rage -in which case it was calculated- OR whether you think she was psychotic -in which case she probably wouldn't have been aware of who or what she was shooting at.
So being in a " psychotic " state,Sheila would have calmly ambled along ? The very fact that she had hold of a firearm was an intention to do damage in some way or she wouldn't have done it. We'd all like to think that she'd been in a psychotic state,but anger also plays a part in a state of psychosis where the patient hasn't been medicated sufficiently or they wouldn't display these outbursts.
Anger does take over as in Sheila's case she'd have been mulling over her life in general and looking for the cause which had been at WHF.
What I'd be wanting to see ( written doc. ) is whether she ever spoke of suicide because those with a depressive or even a psychotic tendency don't always kill themselves after killing others.
Something that JM had said to Jeremy reflects what Sheila was thinking about her boys and that was " if I can't have you nobody else can " or words to that effect when JM put a pillow over JB's face,except that Sheila shot her children.
By all accounts,it's been said many times that Sheila appeared normal that day,though quiet that evening when she'd said very little to her aunt on the phone. Normal ? Yes or no ?