A tuna fisherman caught a feeding frenzy on camera Thursday as three great white sharks feasted on a whale carcass in Cape Cod Bay.

Frank Duggan sent the video to WFXT, showing the sharks circling the carcass and furiously tearing meat from it.

"You could tell by the video, heart rates were moving at that point," Duggan said. "When that first big one came up, it was a little overwhelming at first."

Duggan, captain of Outer Limits II of Quincy, Massachusetts, had set out with his buddies early Thursday morning.

"Look at it! Look at the size of its head!" the men are heard saying excitedly in the video. "Feeding time!"

The Atlantic Great White Conservancy shared Duggan's video on Facebook. The non-profit tracks tagged sharks, but Duggan said he didn't see any tags on the sharks.

Duggan estimated the biggest shark was about 16 feet long - longer than the width of his boat.

"Once in a lifetime thing to see three great whites all together like that in this part of the country," Duggan said. "I hope I get to see it again some day, but I have my doubts."