Leo Ryan was a Democratic Congressman. He served with the U.S. Navy from 1943-46 as a submariner, and graduated from Nebraska's Creighton University with an A.B. and an M.S. He was a high school history teacher, later serving as a South San Francisco city councilman from 1956 to 1962, then was elected mayor of South San Francisco. Less than a year later, he was elected to the California State Assembly, and in 1972, he was elected to the U.S. House of Representatives for the 11th Congressional District of California.

In 1978, reports regarding the Peoples Temple, led by cult leader Jim Jones, began to filter out stories of abuse and human rights violations. Ryan decided to go to Jonestown, the Peoples Temple's main enclave, to investigate.

In November 1978, Ryan and his staff arrived in Georgetown, Guyana. For three days, Ryan negotiated with Jones' legal counsel and held meetings with embassy and Guyanese officials. Finally, Ryan and several aides boarded a small plane to the Jonestown compound. Initially, the welcome at Jonestown was warm, but after only a few hours Ryan and his entourage began receiving notes and requests to leave. The next morning, Ryan and his aides continued their interviews, and met a woman who secretly expressed her wish to leave Jonestown with her family. The group wishing to leave departed Jonestown and arrived at the airstrip. Peoples Members then ambushed the group and opened fire, killing Congressman Ryan and four others, wounding another nine.

The following day, the Guyanese army, ordered to arrest Jones and disarm Jonestown, cut through the jungle to reach the settlement, and discovered all 900 of its inhabitants dead. Leo Ryan's body was returned to the United States and is now interred in Golden Gate National Cemetery in San Bruno, California. He was posthumously awarded a Congressional Gold Medal. He is the only member of Congress to have been killed in the line of duty.