Beach-goers yelled "shark" and "get out of the water" and lifeguards ran to help in the chaotic scene that unfolded on a Cape Cod, Massachusetts, beach Monday when a shark attacked a seal dangerously close to swimmers and surfers.

As blood spread on the ocean surface just yards from shore at Nauset Beach near Chatham, people on the beach began to panic, believing at first someone had been killed, according to NBC New York.

Two teenagers from New York surfing for the first time were among those who panicked, calling for help as they had difficulties swimming in while attached to the surfboard's leash, the Boston Globe reported.

Lifeguards and two beachgoers, including Pat O'Brien, who had just gotten out of the water with his daughter, ran to help them.

The teenagers were identified as Nisi Schlanger of Brooklyn (also referred to has Schlinger and Scholonger in reports) and Zevi Greenspan of Crown Heights. They were feet away from the shark attack.

"I look on the left and I see my friend Nisi paddling for his life and I see something flubbering in the water with blood all around it," Greenspan told New England Cable News. "I thought it was a person."

Greenspan told NBC New York, "I just swam for my life right there, just dreading the moment the shark was gonna pull me in and suck me in."

Added Schlanger, "I was just, like, pulling my board, and people were yelling, 'Get out of the water, get out of the water!' I thought I was dead."

In the chaotic scene, lifeguards ran to help two teenage surfers who struggled to get out of the water.

When O'Brien heard "shark," he and his 9-year-old daughter headed for shore.

"I turned to my left, and I could see [the seal] and I could hear it," he told the Boston Globe. "The seal was making a lot of noise, like it was screaming. I've never seen so much blood in my life."

Of the boy he helped to shore, O'Brien said, "I'll never forget the look on his face."

After the incident, Nauset Beach was closed indefinitely, as were Ballston, Longnook, Coast Guard and Head of the Meadow beaches after a spotter plane located a shark close to shore.

O'Brien's sister, Meg, who witnessed the chaotic scene and shot video, reported to the Globe that the seal managed to escape the shark but bled to death on the shore farther down the beach.

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