An orca was spotted off the coast of Cape Cod on Monday.
According to the New England Aquarium, the sighting of an orca, or killer whale, is extremely rare in this area.
Researchers at the New England Aquarium discussed the orca sighting on Tuesday afternoon.
The male orca was spotted by Bruce Peters, a tuna fisherman with Capeshores Charters, on Monday afternoon, about 13 miles off shore near Chatham, Massachusetts.
"I'm 60 years old, have been fishing my entire life, and I've only seen them twice in my life. I was surprised," Peters told the Boston Globe.
Phillip Hamilton, one of the aquarium researchers, described the sighting as "pretty rare." He added that these whales are more common on the Eastern side of the northern Atlantic ocean.
There are less than 100 that have been photographed and identified.
Alisa Schulman-Janiger, a marine mammal expert with NOAA, identified the orca as "Old Thom," who had been spotted several times between 2008 and 2015.
One person said he saw the orca off the coast of Portland, Maine, last week. Another person said he saw the animal chasing prey off Wellfleet early Tuesday.