WASHINGTON — Men and women in dark suits and uniforms milled around the National Law Enforcement Officers Memorial on a humid, hot early July morning.

Some sought shelter from the blazing sunshine. Most of them were Secret Service employees gathered at the tree-lined, granite shrine inscribed with the names of officers and agents who died while giving their last full measures of service to the nation.

The agency celebrated its 150th birthday on July 5, but paused on this day to honor its fallen.

“Our agency is a unique institution in that we must be prepared for the worst-case scenarios at every moment, every day, but nothing will ever prepare us for the loss of a colleague,” said Secret Service Director Joseph Clancy.

Below is a list of those who’ve died in the line of duty, beginning with Operative William J. Craig, who died Sept. 3, 1902, in Pittsfield, Massachusetts, after a collision between a street car and President Theodore Roosevelt’s carriage.

Secret Service officers who've died in the line of duty