He was at the White House on April 14, 1865, when his father was shot at Ford’s Theater. He rushed to the Petersen House where the President was taken to be treated and was there the next morning when his father died.
Sixteen years later he was serving as Secretary of War to President James Garfield. On July 2, 1881 Lincoln was with President Garfield at the Sixth Street Train Station in Washington, DC when the President was shot by Charles Guiteau. Garfield died two months later.
Twenty years after that, Lincoln was a guest of President William McKinley at the Pan-American Exposition in Buffalo, New York, when the President was shot by Leon Czolgosz on September 6, 1901. McKinley died 8 days later.
These events caused Lincoln to believe he was bad luck, and he thereafter refused to attend state events or accept Presidential invitations.