Clayton began his USDA career at Honolulu International Airport with Plant Protection and Quarantine (PPQ) as a part-time employee while finishing his degree in tropical horticulture. His first full assignment was at John Fitzgerald Kennedy International Airport in 1977. Clay returned to Honolulu International Airport soon after. In 1980, he promoted and moved to Los Angeles International Airport, and shortly thereafter he was promoted to Facility Operations Director. On April 22, 1998, USDA Facility Operations Director Iijima and Entomology Supervisor Morley M. Suzuki met with a subordinate employee. At some point during the meeting, the employee shot and killed Iijima and Suzuki before turning the weapon on himself. No clear motive for the shootings was given.