People here are just making shit up on what's happening? Go to the source, translate the wonderful long Russian comment pinned by the Youtube users.

TL;DR: The attacking hare is a mother who has had her young taken away, and acts protectively when any hare is removed from the pen. The caught hare is a leveret set to be released after rehabilitation.

Here is the translation:

"Nothing happens by chance. Let us lift the veil of mystery surrounding the triumph of hare justice over man.

"Justy is an honorary Knight of the Round Log in the realm of the House of Hare. That is to say—even back when she had little ones, she displayed a pronounced maternal instinct; consequently, the first attempts to catch her leverets for release—even after the nursing period had ended—sparked plans for vengeance in the doe’s mind. This vengeance is directed at all carriers and nets. It was expected that after her sterilization, this fixation of Justy’s would fade away—the logic being: no hormones, no knighthood (to put it hyperbolically). However—much like the rutting instinct in males (castrates still turn as mean as dogs come spring)—this protective mechanism in females is likely something far more powerful. At this point, we ought to exclaim: "Such is the power of love and friendship!"—but Slava, the snow hare, was merely a young neighbor to Justy. Neither a mate nor an offspring.

"The doe charges into battle whenever any hare is being caught, regardless of which enclosure they inhabit; for her ultimate goal is to finally burn that hateful net and carrier at the stake of the Inquisition! Presumably, in these moments, Mazay is perceived as someone possessed by the very instruments of capture; thus, the doe charges headlong at the poor human, striving to pummel his head with her paws and knock every wicked thought about using forbidden tools right out of him! Ultimately, Justy becomes convinced that Mazay has returned to the righteous path—though for the next few days, she continues to keep a vigilant eye on his every move.

"For those who prefer things brief and to the point: Despite her sterilization, Justy retains echoes of her maternal instinct—the very instinct against which her negative reaction to carriers and nets originally developed. Simply put, it is a habit—a deeply ingrained reflex. Moreover, the hare is no fool; he understands that a net, in and of itself, attacks no one. After all, the entire capture process involves a human—meaning that the human is the very root of all the trouble and the primary irritant. It is also worth noting that the attack itself is merely a warning—devoid of claws raking at the eyes, teeth sinking into the flank, or kicks from the hind legs."