How old was Lincoln when he was shot?

There is an odd coincidence in regard to Robert Todd Lincoln and presidential assassinations. The night his father was shot, Lincoln was invited to accompany his parents to the theater, but declined. When President Garfield was shot in a Washington, D.C. train station in 1881, he was present at Garfield's invitation. When President William McKinley was shot at the Pan-American Exposition in Buffalo, New York in 1901, Lincoln was present at McKinley's invitation. However, he was not an actual eyewitness to any of these assassinations. After McKinley's death, Lincoln let it be known that he wanted no further invitations from any US president, as three of them had invited him to be present at their assassinations.