Have orcas ever been observed to be eaten by another species?

Orcas are well known to prey on just about everything that lives in the ocean, even including great white sharks. Yet in a lot of cases I know that the food chain is not unidirectional, there are many cases where even so-called apex predators will get attacked and eaten if they are weak and let their guard down (the eternal rivalry between lions and spotted hyenas comes to mind).

My question is this, are there any known cases of orcas being killed and eaten by another non-orca marine mammal (i.e., not humans)? Such as a lone adult without a pod being attacked, or a calf being taken when it’s mother wasn’t looking?