A look at some accidents that have resulted in deaths of officers traveling in the president's motorcade:
1902 — Secret Service agent struck and killed by trolley car in Lenox, Mass., while serving in President Theodore Roosevelt's detail
1928 — Police officer on motorcycle escort to presidential candidate was struck and killed in Kearny, N.J.
1929 — Virginia State Police officer dies about six weeks after a motorcycle crash while escorting President Calvin Coolidge
1992 — Palm Beach County Sheriff's deputy dies in motorcycle accident while escorting Sen. Paul Tsongas, a presidential candidate
2006 — Honolulu Police officer dies after his motorcycle slides on a rain-slicked roadway, where he was escorting President George W. Bush
2007 — Rio Rancho, N.M., police officer dies in motorcycle crash while escorting Bush's motorcade
2008 — A Dallas police officer slams into a guardrail and is killed while escorting then-Sen. Hilary Clinton's motorcade
2012 — Jupiter, Fla., police officer dies in crash while President Barack Obama travels to campaign rally
Sources: National Law Enforcement Officers Memorial Fund, Associated Press News Research Center, news archives.