Will a mouse murder its young without eating it?

I just got back from a trip, and I opened up my sock drawer, and inside was the decaying, horrific remains of a dead baby mouse, or possibly rat. It was still nearly bald, with sparse gray hair just starting to come in. I had seen where mice had nested in my drawers before, with little pieces of paper and cotton piled in the corner, underneath the clothes. This baby mouse was drug to the top of the pile of the clothes, away from the nest. A trail of blood was running across the tops of the clothes, and, get this, the mouse was just laying there, completely intact, except for a big hole gnawed in the side of its skull, and it looked as though its brain was completely removed. Also nearby it was a small hunk of meat. I don't know if it was the animal's brain, or maybe some of it's innards, or even just the remains of another baby that was almost entirely eaten. I didn't get a chance to examine it before my dad threw it out. Now I know mother mice will kill their babies and eat them if they are extremely sick, or kill them and remove their bodies somewhere else, but this baby was only moved to the top of the pile of socks that the nest was under, which would be senseless if the mother was trying to protect the rest from disease. Other than its mother, I can't imagine what else could have gotten in there and killed it. The only other detail I find very relevant (and I have a pretty lucid imagination :)), is that in the drawer I also had a bag of an herb called "mugwort". It has interesting drug properties, and is used to give you very intense visual dreams. You can smoke it or ingest it toward that end, but it works just as well to be near some while you are sleeping, and believe me, IT WORKS. I'm wondering if maybe the dreams had an awful psychological/spiritual effect, and could have driven the mother a bit crazy and made her kill her offspring with no apparent genetic or hygienic benefit. Or is this something mice and other rodents are known to do for some other reason? I would appreciate an open minded answer to this. Thanks.