William Lytton of Scarsdale, New York, was about 30 yards from shore, surrounded by about 10 seals, when he was bitten on the left leg and left side of his abdomen by a shark, leaving deep puncture wounds, the Cape Cod Times reported.
Lytton stumbled back to shore, leaving a trail of blood behind him, where he was found by Molly Tobin of New York, a vacationer who had just arrived at the beach with her friends.
"We were the first people to take care of him," she told the Cape Cod Times, noting that appeared to be okay but was lying by himself on the beach.
"Then we saw the wound," she said. "It was definitely a shark bite to his leg, on the left side."
Tobin tried to stop the bleeding with beach towels from other beachgoers while someone ran inland to get better cell phone service in order to call 911. The group moved Lytton closer to the road, where paramedics received him and evacuated him to Tufts Medical Center in Boston.
The last time someone was bitten by a shark in Massachusetts was in 2012, Boston.com noted, and the last time someone died of a shark attack in the state was in 1936.
"They're there, just as much as the sunrise and sunset," vacationer Steven McFadden, of Plattsburgh, New York, told Boston.com regarding the sharks. "We're just guests."
CBS Boston station WBZ posted aerial footage Thursday of a shark in the water in the vicinity of where Lytton was bitten, speculating it was the shark that attacked him, although that has not been confirmed. One commenter replied to the tweet, noting that "shark in the Atlantic Ocean" isn't exactly breaking news.
Dr. Gregory Skomal of the Atlantic White Shark Conservancy said the type of shark had not yet been confirmed, noting that the region's great white shark population has grown rapidly in recent years due to the growing seal population. Seals are some of great whites' favorite meals.
Cynthia Wigren, CEO of AWSC, said in a statement Wednesday night, "While we still don't know all of the details of this particular bite, sharks are not known to target people specifically, and when they do bite people, it's usually a case of mistaken identity."
Truro Fire Chief Timothy Collins said Wednesday he was hopeful Lytton would recover, given that he was conscious and talking at the time he was evacuated.
Truro town staff have since placed a "Danger, No Swimming" sign at the beach, which does not have lifeguards, according to the town's website.