Richard Marcinko, first commanding officer of Seal Team 6, dies on Christmas Day

Author and former U.S. Navy SEAL Richard Marcinko arrives at Sapphire & Day Club on Aug. 1, 2014, in Las Vegas, Nevada. (Photo by Gabe Ginsberg/FilmMagic)

Richard "Dick" Marcinko, who was the first commanding officer of U.S. Navy SEAL Team 6, died Saturday at the age of 81, according to an announcement from his son.

"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," tweeted Matt Marcinko on Sunday. "His legacy will live forever. The man has died a true legend. Rest In Peace Dad. I love you forever."

Marcinko's passing was also announced on the Navy SEAL Museum's Facebook page, which said, "Dick Marcinko played a very unique part in SEAL history, leaving a legacy like no other. ‘Demo Dick’ is considered the United States’ premier counterterrorism operator. We send our deepest sympathies to his family, teammates, and friends."

Marcinko was born Nov. 21, 1940, in Lansford, Pennsylvania, and enlisted in the U.S. Marines before being rejected for his lack of a high school diploma. He later enlisted in the U.S. Navy in 1958, eventually working his way up the rank of commander. He would also go on to earn a bachelor's degree and master's degree in international relations and political science, respectively.

He was the first commanding officer of both SEAL Team 6 and RED CELL, two the military's top counter-terrorist units, which he helped to found.

Marcinko deployed to Vietnam in January 1967 in 2nd Platoon, SEAL Team 2. He participated in the May 18, 1967, assault on Ilo Ilo Hon, which the Navy has described as its most successful SEAL operation during the Vietnam War.

After returning to the United States, Marcinko deployed to Vietnam for a second time, during which he participated in the Tet Offensive.

The North Vietnamese placed a bounty on Marcinko's head because of his effective leadership, but he evaded the enemy. He would go on to earn four Bronze Stars, as well as the Silver Star and the Vietnamese Cross of Gallantry. Altogether he earned 34 citations and medals.

The second wave of combat helicopters of the 1st Air Cavalry Division fly over an RTO and his commander on an isolated landing zone during Operation Pershing during the Vietnam War. (Photo by Patrick Christain/Getty Images)

After serving as one of two Navy representatives on an unsuccessful task force intended to free American hostages during the Iran hostage crisis in 1979, Marcinko was tapped to design and lead an elite counterterrorism team, which later became SEAL Team 6. The name was intended to fool the Soviet Union and other adversaries into thinking that the U.S. had more SEAL teams than it did.

Marcinko commanded SEAL Team 6 from August 1980 to July 1983. He was also the author of several books, including his 1993 New York Times bestselling autobiography, "Rogue Warrior." The book would lead to several spinoff novels.

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"The SEALs who knew Dick Marcinko will remember him as imaginative and bold, a warrior at heart," retired Navy SEAL Adm. Eric Olson told Navy Times. "He was a spirited rogue for sure, but we are better off for his unconventional service."

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