The victim in his mid-20s died in hospital from his injuries, said Wellfleet police officer Michael Hurley.
"Life saving measures were attempted on beach", state police spokesman David Procopio said in an email.
The beach was closed to swimmers but the type of shark involved in the attack is not yet known.
Beach-goers carry a shark attack victim down Newcomb Hollow Beach.
Witnesses say the man was boogie boarding with a friend when the shark aggressively attacked.
Chris Hartsgrove, acting deputy chief of Cape Cod National Seashore, said the injuries appeared to be from a shark. Booth said. "It was like right out of that movie Jaws".
The most recent shark attack before Truro happened in 2012, when Christopher Myers suffered deep lacerations on both legs after an encounter with a great white.
The attack is being investigated by State Police and the Cape and Islands District Attorney's office.
August 17: Coast Guard Beach in Eastham and Coast Guard Beach in Truro are closed because of shark sightings.
The attack comes just weeks after a man from NY was severely injured in a shark attack on August 15 at Long Nook Beach in Truro.
Newcomb Hollow Beach was closed after a fatal shark attack on September 15, 2018.
"We've been surfing all morning right here and they were just further down", she said of the two boogie boarders.
Wendy Northcross, CEO of the Cape Cod Chamber of Commerce, said the Cape doesn't have a lot of experience in how to manage these shark attacks.
Barnstable county commissioner Ron Beaty said he had warned something like this could happen. Great White Sharks are predators and should be considered risky. He said those officials were responsible for "this frightful shark attack" due to lack of attention and inaction.