Warning: Orcas close in seal for feeding time in moment rarely caught on video

ALASKA, UNITED STATES - 2015/08/24: Orca (Killer whale) spyhopping off Wrangell Island, in Southeast Alaska, USA. (Photo by Wolfgang Kaehler/LightRocket via Getty Images)

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ALASKA, UNITED STATES - 2015/08/24: Orca (Killer whale) spyhopping off Wrangell Island, in Southeast Alaska, USA. (Photo by Wolfgang Kaehler/LightRocket via Getty Images)

In a moment rarely caught on video, KIRO's Chopper 7 flew over orcas as they closed in on a seal for feeding time.

Two groups of orcas frequent northwest waters: transients and residents. Transient, mammal-eating orcas became familiar with northwest waters in record numbers last year.

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Warning the video may be disturbing for some.

Scientists and whale watchers reported that a boom in the pinniped population -- seals and sea lions -- last year meant a set table for the orcas.

>> Related: Transient orcas visit northwest waters in record number

Pacific Whale Watching Association reports the orcas, also called Bigg's killer whale T60D, are all business at mealtime, coming onto the scene swiftly, in small groups and without a sound.

About 320 individually identified transient killer whales swim along the West Coast of North America.

Resident orcas’ diets mostly consist entirely of chinook salmon—a food source that’s population has been cut in half since the 1980s. As of last year, there were only 79 resident orcas left.