Deer have a much more varied diet than most people think they do, but it is still rare to catch the critters eating something strange on video. Believe it or not, deer will readily eat meat if desperate enough. Most of this strange carnivorous behavior is isolated to the winter months, when a deer may munch on a frozen squirrel or two, but the animals have been documented to consume live prey. In the below video, a deer eats what appears to be a swallow.
Keep in mind, deer lack the teeth of more accomplished carnivores and and chew meat much like they consume their usual forage. Read here for more about the meat-eating habits of deer.