The Feeding Frenzy

Normal people, even good people, can get caught up in the dynamic. In law enforcement, we call it a "feeding frenzy." Usually rookie officers, seeing a Use of Force and still eager to prove themselves, will jump in, which is fine. Usually, the more officers involved, the less risk of injury. However, if one officer escalates the Use of Force to a higher level than is justified, others may follow suit. If one continues after the threat is restrained, others may follow suit.

--Rory Miller, Meditations on Violence, p. 50.

(The relevant portion of the video begins about 1:20).