Here's some background information about violence against US politicians and diplomats throughout history.
Presidents: January 30, 1835 - President Andrew Jackson is shot at by Richard Lawrence as he attends a congressional funeral in the Capitol in Washington. Lawrence fires twice, but the bullets do not discharge.
April 14, 1865 - President Abraham Lincoln is shot and killed by John Wilkes Booth during a performance at Ford's Theatre in Washington.
July 2, 1881 - President James Garfield is shot by Charles Guiteau as he is about to board a train at the Baltimore & Potomac Railroad Station in Washington. President Garfield is severely wounded and dies on September 19.
September 6, 1901 - After delivering a speech at the Pan-American Exposition in Buffalo, New York, President William McKinley is shot in the stomach by Leon Czolgosz. McKinley dies of his wound on September 14.
October 14, 1912 - Former President Theodore Roosevelt, while campaigning as a candidate of the Progressive Party, is shot and wounded by John Schrank while on his way to a campaign appearance in Milwaukee, Wisconsin.
February 15, 1933 - President-elect Franklin D. Roosevelt is shot at by Joseph Zangara while sitting in his open air car after addressing supporters in Miami, Florida. Roosevelt is not harmed.
November 1, 1950 - Two Puerto Rican nationalists, Oscar Collazo and Griselio Torresola, try to shoot their way into Blair House, where President Harry Truman is staying while the White House is renovated. The gunmen never reach the interior of Blair House and Truman is not harmed.
September 5, 1975 - Charles Manson follower Lynette "Squeaky" Fromme attempts to shoot President Gerald Ford in Sacramento, California. Secret Service agents grab her and the gun, and Ford is unhurt.
September 22, 1975 - Sara Jane Moore, a woman with ties to left wing radical groups, attempts to shoot President Gerald Ford in San Francisco.
March 30, 1981 - President Ronald Reagan is shot and wounded by John Hinckley Jr. as he leaves the Hilton Hotel in Washington after delivering a speech to the Construction Trades Council.
Congressmen and Senators (selected): December 22, 1867 - Rep. Cornelius Hamilton (R-OH) is shot and killed by his mentally ill son in Marysville, Ohio.
October 22, 1868 - Rep. James Hinds (R-AR) is shot and killed by Ku Klux Klan member George Clark while traveling on horseback to a speaking engagement near Indian Bay, Arkansas.
April 24, 1905 - Rep. John Pinckney (D-TX) is shot and killed at a Waller County Prohibition League in Hempstead, Texas.
September 8, 1935 - Sen. Huey Long (D-LA) is shot in the State Capitol in Baton Rouge, Louisiana. Long dies two days later from the wound to his abdomen.
March 1, 1954 - Rep. Alvin M. Bentley (R-MI), Rep. Clifford Davis (D-TN), Rep. Ben F. Jensen (R-IA), Rep. George Hyde Fallon (D-MD), and Rep. Kenneth A. Roberts (D-AL) are wounded when four Puerto Rican nationalists enter the Capitol and open fire from an upstairs spectators' gallery onto the House floor.
June 5, 1968 - Sen. Robert F. Kennedy (D-NY) is shot by Sirhan Sirhan at the Ambassador Hotel in Los Angeles, following his victory speech after the California Democratic presidential primary. Kennedy dies the next day.
November 18, 1978 - Rep. Leo Ryan (D-CA) is shot and killed at an airstrip in Guyana after investigating the activities of the People's Temple led by Rev. Jim Jones.
January 8, 2011 - Rep. Gabrielle Giffords (D-AZ) is shot and wounded by Jared Lee Loughner at a political event outside a Safeway supermarket in Tucson, Arizona. Six people are killed.
June 14, 2017 - Rep. Steve Scalise (R-LA), the House majority whip, is shot in Alexandria, Virginia, during a Republicans' baseball team practice. Two others on the congressional team, and two Capitol police officers are also shot. The gunman James Hodgkinson is killed by authorities.
Governors and Mayors (selected): February 15, 1933 - Chicago Mayor Anton Cermak is killed in Miami, with a bullet meant for President-elect Franklin D. Roosevelt. He dies on March 6.
May 15, 1972 - Alabama Governor George Wallace is shot by Arthur Bremer while campaigning for president in Laurel, Maryland. Wallace is paralyzed from the waist down.
November 27, 1978 - San Francisco Mayor George Moscone and Board of Supervisors member Harvey Milk are murdered by Dan White.
December 10, 1986 - Mount Pleasant, Iowa Mayor Edward King is shot and killed by Ralph Davis at a city council meeting.
February 7, 2008 - Kirkwood, Missouri Mayor Mike Swoboda and six others are shot when Charles Thornton opens fire at Kirkwood City Hall. Swoboda passes away seven months later due to complications.
Ambassadors: August 28, 1968 - US Ambassador to Guatemala John Gordon Mein is killed by guerrillas in Guatemala City, Guatemala.
March 2, 1973 - US Ambassador to Sudan Cleo Noel Jr. is killed by Palestinian militants at the Saudi Arabian embassy in Khartoum, Sudan.
August 19, 1974 - US Ambassador to Cyprus Rodger P. Davies is shot and killed during a protest outside the US embassy following the Turkish invasion of Cyprus.
June 16, 1976 - US Ambassador to Lebanon Francis E. Meloy Jr. is kidnapped and murdered by Palestinian militants in Beirut, Lebanon.
February 14, 1979 - US Ambassador to Afghanistan Adolph Dubs is kidnapped and killed by militants in Kabul, Afghanistan.