https://www.yahoo.com/entertainment/boy-6-constantly-smiling-killed-154205872.html
I bet daughter was a single moo with a couple from the town meth head and she dumped them on the grandparents. Grandmoo probably was desperate to get a redo and the sprogs were probably terrors from hell and grandpa went nuts.
Either that or moo depended on grandparents to babysit as many do and this is how they found out grandpa was getting dementia which can lead to violence