Answer :

Four Presidents have been assassinated, and these are;
-Abraham Lincoln was assassinated on Friday the 14th April 1865, at 10:15pm by John Wilkes Booth. He was The 16th President of the United States, and the first president to be assassinated.
-James A Garfield was assassinated on Saturday 2nd July 1881, at  9:30am by Charles J Guiteau. He was the 20th President of the United States, and the second to be assassinated in the space of less than 20 years.
-William McKinley was assassinated on Friday 6th September 1901,at 4:07pm by Leon Czolgosz. He was the 25th President of the United States, and the third president to be assassinated.
-John F Kennedy was assassinated on Friday 22nd November 1963 at 12:30pm by Lee Harvey Oswald (Although this is still suspicious). He was the 35th President of the United States and was assassinated most recently.
Hope this helps :)