Mark Otho Sullivan, 80 of Great Falls, a retired Air Force Tech Sergeant, died Thursday, August 9, 2012 of natural causes at a care facility in Missoula.A memorial service will be held at Hillcrest Lawn Mausoleum on Saturday, August 18, 2012 at 10 a.m.Schnider Funeral Home is handling arrangements.Mark was born July 12, 1932, in Lawler, Iowa to Carl and Marjorie Sullivan. After high school graduation, he entered the US Navy for four years and retired after 20 years in the Air Force as a Tech Sergeant. He married Nancy Baumann on November 4, 1967 in Helena.In the Boy Scouts of America, Mark was an avid troop leader, member of the Order of the Arrow and one of a few Americans to be a member of the Canadian Order of the Tomahawk.He was also active in the United Ostomy Association.Mark was a devoted family man who took great pride in his roles as a father and husband. He was a friend to not only those close to him, but also to strangers who needed a helping hand. As an avid Boy Scouter, he influenced the lives of countless young Scouts over a span of 40 years in both the United States and Canada.In Marks free time he enjoyed many outdoor activities, his construction business and giving his time to various projects in the community.Mark is survived by his son Shane Sullivan, his wife Sue and their children Jake and Nora; daughter Stacey Hansen, her husband David and their children Grace and Jordi; and daughter Shiloh Hanley and her husband Joshawa.He was preceded in death by his wife, Nancy; his parents, Carl and Marjorie; and sister, Becky.Memorials are suggested to United Ostomy Association, PO Box 512, Northfield, MN 55057-0512.