Anyone with any brains would know that deers leg was injured before that dog came along... We have a lab mix mutt that is a hell of a runner, he catches quite a few snowshoe hares... He doesn't stand a chance of catching a healthy deer. And yes, he does chase them when he see's them, but the chase doesn't last long, he's always back in less than a minute.
Did you know you can tell what a dog is thinking by which side it wags it tail? Yup.. If a dogs tail is wagging mostly left, its in danger/protect/fear mode.. wags mostly to the right its playful/fun/happy....
I caught a story about a study on dog behavior the other day that showed how dogs react to that... Right down to their increased heart rate. I wondered who was funding it.
They would also faint if they saw how a wolf operates.
Yup, they may even lose their lunch... This is how wolves operated on my 100lb dog