My rats get all sorts of table scraps.
A side note- I was rat sitting for a friend who fed generic Publix dog food to her colony. Pinks were born after she moved them to my place and they grew to weanling before one of the rats decided to kill (not eat, just maul) them all. A second time I was taking my own weanlings to a friend for feeders and picked up some of her adults. I put them in the same bin and one of her rats mauled the weanlings. I didn't think it would happen again and my rats would have never done that. I still feel horrible.
I think her rats are either messed up because of the low quality dog food, or just have bad genetics. If I were her, I would start the colony over.
In your case, I would just make note of what rat did it, and feed it off if it happens again.