Commenter-
“Simple explanation for the deer’s behavior - The deer is a doe. She probably has a fawn hidden in the area. The screaming a rabbit makes when it is frightened sounds very similar to the bleating a young fawn does when it is attacked or frightened. The doe heard the rabbit, assumed it was her fawn under attack, came to defend it and didn’t care that it was a rabbit. The doe was triggered and went for the cause of the attack - the hawk.”
Sounds plausible to me.
Just a little side comment. About 25 years ago, while deer hunting with my dad, I saw an owl flying through the woods early one morning. It was just getting light and it was still very quiet. I watched the owl fly from my left to my right, disappearing in the thick trees about a hundred yards away. Suddenly, I heard the most horrendous and horrific "screaming". This went on for about 30 or 45 seconds until all fell quiet again. A few moments later I saw the owl flying back across the woods, holding a rabbit in his talons. I'll never forget the sound of that "screaming". Very unsettling.
Once in Nevada I had a good view of a golden eagle attacking a fawn. A doe charged down the hill and chased the eagle away. The fawn left with its mother.
I saw a buck in a video act like that .... a “hunter” aka Darwin Award candidate, had sprayed doe urine on HIMSELF to attract a buck. He attracted one, all right - big boy knocked him down on his back and proceeded to try to gore him ... hunter grabbed antlers and was holding on for deer life (pun intended) and then the deer started stomping him - it would back off slightly, then start goring/stomping again. He was kicking at the deer with his legs - the deer was royally po’d.
The general public does not realize how a deer will use its legs/hooves for defense and the hooves are sharp!
I do a lot of varmint hunting, mostly coyotes and I can’t count the number of times I’ve had deer come running in using the jack rabbit or cottontail calls. If you’d like to see this on video check out CARNIVORE on the Pursuit channel we catch it on video quite often. New season just started.