I don't see the rats acting to relieve their own stress as all that different to empathy. Certainly if they're experiencing empathy it will be distressing to see another creature suffer.

A few days ago, Bella grabbed a galah that was already grounded for some reason. It was a terrible few seconds while I freed the bird from her grasp by yanking her off it. In addition to the bird's distress cries, which I can only describe as screams, were the cries of the birds in the trees above us. I noticed for the rest of the walk that two other birds - not galahs or the usual magpies - appeared to swoop at Bella, almost with a sense of "We know what you did," about it. Or maybe I was just projecting that last bit.

The galah was still down and alive when we came back but I suspect that Bella wasn't the first large animal to violate it that day and, afterwards, it may well have gone off somewhere to die. Poor thing.