(CNN) Richard Marcinko, a legendary military figure known for leading SEAL Team Six when the covert special operations unit was in its infancy, died Saturday, according to his son and the National Navy SEAL Museum. He was 81.
"Last night, Christmas evening, we lost a hero, who's also known as The Rogue Warrior, the retired Navy SEAL commander AND the creator of SEAL Team Six, my father, Richard Marcinko," Matt Marcinko wrote in a tweet on Sunday.
"His legacy will live forever. The man has died a true legend," he added.
Richard Marcinko, a combat veteran of the Vietnam War, was the first commanding officer of SEAL Team Six, the secretive unit formed in 1980 that would later carry out the operation that killed Osama bin Laden in Pakistan in 2011.
Marcinko designed and organized SEAL Team Six after the failed hostage rescue attempt in Iran during the Carter administration, according to a social media post from the Navy SEAL Museum.
After his retirement from the Navy in 1989, Marcinko became an author, public speaker and consultant, according to The New York Times. But he was also a controversial figure -- having been convicted of military contract fraud, the Times said.
In today's military, many regard him as a rogue operator, according to the Times. He is also considered a "premier counterterrorism operator," as the SEAL Museum, which is not connected to the US military, described him in a statement on Sunday.
The museum, which called him "Demo Dick," said he led SEAL Team Six from August 1980 to July 1983.
"At the time, the Navy had only two SEAL Teams. Marcinko named the unit 'SEAL Team SIX' in order to fool other nations, notably the Soviet Union, into believing that the United States had at least three other SEAL Teams that they were unaware of," the museum said, adding that Marcinko "hand-selected the Team's members from across the existing SEAL Teams and Underwater Demolition Teams."