The Facebook page of the Navy SEAL Museum in Ft Pierce, Florida, is reporting that the founder of SEAL Team Six, Dick Marcinko, has passed away at age 81. According to a tweet shared by his son Matt, he died on Christmas day.

As reported by the Museum, “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.”

Commander Marcinko was born in Pennsylvania in 1940 and was a high school dropout. Rejected by the Marines for not having a diploma, he was accepted into the Navy as a Radioman rating in 1958. Marcinko applied for and was accepted for SEAL training and joined Underwater Demolition Team Twenty-one(UDT-21) in class 26 in 1961. Marcinko went to college while with UDT-21 and was offered a commission in 1965. The former high school dropout would go on to earn a Bachelor’s degree from Auburn in International Relations and a Masters in Political Science from the Navy Post Graduate School.

Marcinko then went to SEAL Team Two as an officer.

In 1967 Marcinko was with SEAL Team Two, Second Platoon, and led what was called one most successful SEAL operation in the riverine war being waged in the Mekong Delta. In the battle of Ilo Ilo Hon, Marcinko and his SEALs killed an untold number of the enemy and destroyed six sampans used to transport men, weapons, and supplies up and down the Mekong River. His operational successes caught the attention of the North Vietnamese high command, who offered a bounty to anyone who killed or captured him. This bounty was never collected.

He was then made Officer in Charge of 8th platoon on TEAM Two. During the Tet Offensive in 1968, he and his men joined up with Green Berets in the house-to-house fighting at Chau Doc and rescued a group of American nurses caught in the midst of the battle. Marcinko would go on to be awarded a Silver Star, The Legion of Merit, the Vietnamese Cross of Gallantry, and four Bronze Stars, during the course of his career. After this tour, Marcinko would do an eighteen-month stint as the Naval Attache at the U.S. Embassy in Cambodia before returning again to ST-2 as its commanding officer as a Lt Commander from 1974 to 1976,

In 1979 Marcinko would find himself attached to the staff of the Joint Chiefs as one of two naval officers assigned to the Terrorist Action Team or TAT. Here he would be involved in the ill-fated mission to rescue the American hostages held by Iran. The failure of this mission prompted the Navy to develop its first counter-terrorism unit, and Marcinko was put in charge of standing it up.