Before Beauty is two, he witnesses something he says he'll never forget—a hunt. Beauty and the other horses watch as a pack of hunting dogs tear past their field in pursuit of a hare, followed by men on horseback. For a young horse, the noise level is like the equivalent of a rock concert. Beauty, his mom, and the other colts watch as a hare, "wild with fright" (2.7), is chased down and killed by the pack of dogs.
Two horses fall trying to jump a brook to get the hare. Duchess tells Beauty that the horse has broken his neck.
One of the colts says that it serves the hunting horse right, but Duchess disagrees and blames his rider: "I never yet could make out why men are so fond of this sport; they often hurt themselves, often spoil good horses, and tear up the fields" (2.12), she says.
One of the riders is also hurt, badly enough that he's not moving—young George Gordon, the Squire's only son.
Mr. Bond, the farrier (someone who shoes horses), comes to examine the fallen black horse and sees that his leg is broken. Someone goes for a gun and shoots the horse on the spot.
Beauty's mom is really upset, and says she knew the horse, Rob Roy. She's so shaken that "she never would go to that part of the field afterwards" (2.15).
The horses see George Gordon's funeral procession after that, and Beauty comments that all of it was for "one little hare" (2.16). There's some perspective for you.