Swen C. Nielsen immigrated with his family to Utah from Denmark when he was fourteen years old. He attended Provo High School and after graduation joined the Army, where he served as a paratrooper.
Nielsen went into law enforcement, spending three years working for the Los Angeles Police Department’s organized crime unit before coming to BYU and serving for thirteen years as the chief of the university’s police force. In 1974, he became Provo’s police chief. He retired in 1995.
Nielsen married his wife, Shirlene Jones, on April 26, 1956, in the Salt Lake Temple. They were married for fifty-one years and served together as missionaries in the Stockholm Sweden Temple. They had four children: Richard, Bradley, Eric, and Claudia.