America's 20th president, James A. Garfield, was the second chief executive to be assassinated.
PBS website accompanying this series is filled with all the materials you would need to support a lesson on President Garfield with your students. There are background articles that put Garfield's presidency in context, photographs, primary sources, and links to other resources. My favorite linked resource is to the website (curated by the University of Missouri-Kansas City School of Law) that tells the story of the trial of Garfield's assassin.
The PBS video is based upon Candace Millard's Destiny of the Republic: A Tale of Madness, Medicine and the Murder of a President. Millard discussed her book, and the circumstances of Garfield's assassination, in this interview.