The first commanding officer of the U.S. Navy SEAL Team Six, Richard Marcinko has died at the age of 81, according to a statement by his son. Born on November 21, 1940, in Lansford, Pennsylvania, Marcinko was first enlisted in the U.S. Marines but did not make it in due to a lack of a high school diploma. Later in 1958, he enlisted in the U.S. Navy as a  radioman and prospered in the ranks as he made his way up to the positions and became commander.

Marcinko’s son announced the news on Twitter with several pictures of himself with his late father Richard Marcinko, saying, “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. His legacy will live forever. The man has died a true legend. Rest In Peace Dad. I love you forever.”

Later in his life, Marcinko received his Bachelor of Arts degree in international relations majors, from the U.S. Naval Postgraduate School, followed by a Master of Arts degree in political science from Auburn University at Montgomery. His journey with The Naval Special Warfare Development Group commonly known as the U.S. Navy SEAL Team started with SEAL Team TWO in June 1966. He went on to become the first commanding officer of SEAL Team 6, along with RED CELL.

The Navy SEAL Museum shared their own statement of condolence and remorse on the passing of Richard Marcinko saying, “The Museum is very saddened to learn of the passing of Richard “Dick” Marcinko. “Demo Dick” was a retired U.S. Navy SEAL commander and Vietnam War veteran. He was the first commanding officer of SEAL Team SIX.”

Adding, “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,” followed by a huge record of all of Marcinko’s work as part of the U.S. Navy.