Alright, mystery time. I recently moved two female (double and triple checked, the new rat-mate was female) rats together, not knowing that one was pregnant. She had just given birth, and I was separating her from the male for a break, but i guess he got to her before I moved him. Anyway, fast forward a few weeks. Pregger female gave birth to ten healthy rat babies, and neither female was visibly stressed. There were never any fights between the two, and momma never stressed about having her babies with another female in the pen.

Well, I went to check on everyone today because I hadn't had the time to say hello for a day or two (I give everyone enough food and water to last about 3 days.) I opened the tub with the two females to find momma-rat dead, with her innards hanging out. The weird part is that all of her babies were still alive and perfectly fine. My guess is that the kill took place only a few hours before I went to check, because the blood was fresh and wet, and the body had not gone into the rigor mortis state. I removed all ten pups, whose eyes have begun to open (some completely open, some slits) and took out the other female and placed her in a separate cage from the babies. After I cleaned that cage, I moved to the grow-out tub, where I had five small rats. I looked inside to find that two had been recently torn to shreds, and I watched one die. Upon removing the one that had just died, I found nothing wrong with him, no wounds or any internals hanging out. There was a bit of dried blood on his face, which leads me to believe that perhaps the other two carcasses were ill.

I checked my males, and both are fine. I'm currently gassing the three rats who were in cages with bodies, and my mom is nursing the ten babies.

My questions are,
1) What the hell prompted this? It's not a case of starvation, no one was lethargic or sick, and no one was stressed.
2) Why didn't the female who killed the momma leave her babies alive? I doubt it's a territorial issue, because she would have killed the babies sooner.
3) Are the cases related somehow? Can violence between rats spread from cage to cage?
and lastly, 4) The three rats left alive who were in with bodies, will they be safe for my snakes to eat? This is my main concern. Should I cull and dispose of them, or would nothing come of feeding them off?

Thanks for any advice/help in advance.