One of the debated points in ornithology is whether raptors can carry off large prey, even small human children. As Darren Naish points out in this brief note, they can certainly kill large animals. I didn't know the berkut (golden eagle) of Russia had been trained to kill wolves, or that there are records of its American cousin killing cattle (although obviously not flying off with them.)
The most famous and bizarre story of this type is the 1970 report that two large eagles of unknown type, apparently escaped or released exotics from another continent, attacked 70-lb Marlon Lowe of Illinois, and one actually got him off the ground. As crazy as it seems, this event seems to have been real - the clawed boy and his torn clothing were evidence - though I do wonder if the part about actually lifting the child and starting to carry him off before dropping him was a product of the two panicked human witnesses (Lowe and his mother) perceiving things to be even scarier than they were. This would mean Lowe was running as one or both eagles grabbed him and slashed at him, and but his feet may have only momentarily been off the ground. (I will note that Lowe's mother has denied she could have been mistaken on this point, but the physics don't seem to allow for any other answer.) While most accounts of eagles lifting smaller children have been dismissed as folktales, a couple were well-attested and might have happened.