Lincoln was not present at his father's assassination.[50] He was at the White House,[51] and rushed to be with his parents.[52] The president was moved to the Petersen House after the shooting, where Robert attended his father's deathbed.[53]

At President James A. Garfield's invitation, Lincoln was at the Sixth Street Train Station in Washington, D.C., when the president was shot by Charles J. Guiteau on July 2, 1881, and was an eyewitness to the event. Lincoln was serving as Garfield's Secretary of War at the time.

At President William McKinley's invitation, Lincoln was at the Pan-American Exposition in Buffalo, New York, where the president was shot by Leon Czolgosz on September 6, 1901, though he was not an eyewitness to the event; he was just outside the building where the shooting occurred.[54]

Lincoln himself recognized these coincidences. He is said to have refused a later presidential invitation with the comment, "No, I'm not going, and they'd better not ask me, because there is a certain fatality about presidential functions when I am present."[55]

(http://www.autoadmit.com/thread.php?thread_id=4597729&forum_id=2#40707758)