“I conceived of the idea of removing the President four weeks ago. Not a soul knew of my purpose. I conceived the idea myself. I read the newspapers carefully, for and against the administration, and gradually, the conviction settled on me that the President's removal was a political necessity, because he proved a traitor to the men who made him, and thereby imperiled the life of the Republic ... Ingratitude is the basest of crimes. That the President, under the manipulation of his Secretary of State, has been guilty of the basest ingratitude to the Stalwarts admits of no denial. ... In the President's madness he has wrecked the once grand old Republican party; and for this he dies.... I had no ill-will to the President. This is not murder. It is a political necessity. It will make my friend Arthur President, and save the Republic.”
– Charles Guiteau, in his letter to the American people, on 16 June 1881
On July 2nd, 1881, Charles J. Guiteau went to the Baltimore and Potomac Railway Station, and lay in wait for his intended murder victim. President James A. Garfield was scheduled to leave Washington D.C., and Guiteau wanted him dead before his train ever left the city. When President Garfield walked into the waiting room of the station, Charles Guiteau walked up behind him and pulled the trigger at point-blank range from behind. President Garfield cried out: “My God, what is that?”, flinging up his arms. Guiteau fired a second shot, and the president collapsed. One bullet grazed the president's shoulder, while the other struck him in the back. Guiteau put his pistol back into his pocket and turned to leave via a cab that he had waiting for him outside the station, but he collided with policeman Patrick Kearney, who was entering the station after hearing the gunfire. Kearney apprehended Guiteau, and asked him: “In God's name, what did you shoot the president for?” Guiteau did not respond. The crowd called for Guiteau to be lynched, but Kearney took Guiteau to the police station instead. (This paragraph borrows some exact wording from Wikipedia, which I should acknowledge here as a source.)
Contemporaneous depiction of Garfield assassination, with James G. Blaine at right
President Garfield with James G. Blaine in the railway station, shortly after the shooting