Who is Chris Nanos? Pima County sheriff with 50 years in law enforcement heads Nancy Guthrie investigation

The man leading the investigation into the high-profile disappearance of 84-year-old Nancy Guthrie, the mother of NBC "Today" host Savannah Guthrie, is a longtime law enforcement officer with a half-century of experience under his belt.

According to his official biography, Pima County, Arizona, Sheriff Chris Nanos has been an officer of the law since 1976, beginning his career with the El Paso Police Department in Texas. In 1984, he became a corrections officer in Pima County, and the next year was promoted to deputy.