The List murders popped into my head immediately, too.
Interesting that you characterize both sets of murders as stemming from religious mania. I can see that angle. Both men had lost financial control, and were deeply indoctrinated and committed to religious characterizations of the Father as provider and protector.
A question that always arises around patriarchal familicide is "Why did he think he had to take his whole family with him?" This gives a peek into that mindset. I don't want to set anything off here--really, really I don't--but are there any instances of familicide in the Old Testament?
upon edit: Just googled that and no biblical refs popped up; however, I did see it noted that some Christian familicidal fathers have noted their faith in the after-life as a reason for viewing their acts as sanctioned (e.g., Christian Longo, and I think List himself). I don't know though.... I can see that more as deflection from their deeper need to avoid shame.
Yes, me too on the googling around, and yes, List alleged he'd not killed himself along with the family on the promise of "getting together with the family again in heaven" notion - this from a guy who shot his oldest son TEN TIMES. The Old Testament God did command Abraham to kill his son Isaac, something I remember less from my Lutheran catechizing than I do from Mr Bobby Dylan:
Oh God said to Abraham, “Kill me a son”
Abe says, “Man, you must be puttin’ me on”
God say, “No.” Abe say, “What?”
God say, “You can do what you want Abe, but
The next time you see me comin’ you better run”
Well Abe says, “Where do you want this killin’ done?”
God says, “Out on Highway 61”
Ah - love that song. But, really, familicide in the Old Testament would have been a drop in a bloody bucket; here's a list of OT God's going over the top and slaying anyone who so much as looked at Him cross-eyed:
Old Testament Atrocities.
I do believe John List killed his family for his stated reason; yes, he had money problems too, but I doubt he could have led such an apparently conscience-free existence for almost two decades of freedom were he not mentally (and dementedly) "right with the Lord." The jury's out on M. Dupont de Ligonnès's reasoning for his (apparent) rash deed.