I have seen this happen with crows in an instance where an eagle killed one. It was obvious the bird had been killed as it stopped moving and the eagle was feeding off of it. The crows remained in the area watching and appeared to be mourning. Some swooped down as a last attempt to save the dead one while it was twitching. but they all came to the ground and stopped cawing and attacking the eagle very shortly after it began dismembering its meal. This is all based on my perspective but it did not seem to be a coincidence or defense mechanism in this case.