Dang it, I always say ima leave this alone but can’t help itSo now we are getting more information about this.
https://www.yahoo.com/news/dogs-went-drastic-lifestyle-changes-031458173.html
This sounds like they may have been driven mad by neglect and hunger. I can see where if they were desperate for food and unstable from exposure, then found something edible on the walk that mom didn't want them to eat and she tried to take it away from them... she became the meal.
I don't agree with this trainer that a lack of socialization would do this, but isolation in combination with starvation, exposure to extreme temperatures and possibly being left trapped in their own waste could definitely have made them literally insane.
These things could cause this in any dog and probably most humans, too.