A dramatic series of photos showing a wolfpack stalking and killing a calf elk in Yellowstone National Park on September 9, 2010. The pack of 3 wolves chased the elk into the Yellowstone River around dusk, then paced the riverbank for awhile. Then one wolf swam into the river to force it out. The elk spooked and charged upstream in a panic towards the far riverbank where the other wolves were waiting. The elk reached the bank and the chase was on. The elk got about 50 feet on land when the wolves simultaneously pounced on the elk, taking it down. After a minute or so the elk tried one last time to get up but the wolves proved overwhelming and death came quickly. Nature in its raw form--difficult to watch but amazing.