Shark feeding frenzies happen all the time. You just normally don't see one of this size caught on camera.
Fifty to sixty sharks, mostly blacktip and bronze whalers, were filmed by a helicopter off the coast of Perth, Australia. Apparently, baitfish were being fed upon by tuna. The baitfish had massed up into balls to protect themselves, but the whole mass of baitfish and tuna attracted the attention of nearby sharks. Normally, these sharks do not "school", but hunt alone. Nevertheless, a free meal like this was too tough to pass up. Even a huge flock of birds joined the sushi buffet.
Nearby Yanchep beach was closed temporarily, just in case. But, most of the sharks in this frenzy were normally not of concern to humans.
On a separate note, "Feeding Frenzy" was a great live album by Jimmy Buffett. This is not from that.