Under what president did William Cohen serve as Secretary of Defense in the years following the death of Esequiel Hernández Jr.?
Esequiel Hernández Jr.: Esequiel Hernández Jr. (May 14, 1979May 20, 1997) was an 18-year-old American high school student killed on May 20, 1997 by United States Marines in Redford, Texas, located approximately one mile from the United States–Mexico border. William Cohen:  A Republican, Cohen served as both a member of the United States House of Representatives and Senate, and as Secretary of Defense (1997–2001) under Democratic President Bill Clinton.
Bill Clinton