He is the only president to have served four terms in the White House, which makes him the longest serving president in the American history. He is also the last U.S. President to have died of natural causes while holding the office. The assassination attempt on him occurred on February 15, 1933 in Miami, Florida when he was the President-elect and his inauguration was after three weeks. He was giving a random speech from the back of an open car, but remained unhurt. Instead four other people got wounded and Anton Cermak, the Mayor of Chicago was killed due to his injuries two days after Roosevelt’s inauguration. The assassin was Giuseppe Zangara who fired five shots at Roosevelt, but ended up injuring others and killing one. Due to that, he was found guilty of first-degree murder and was executed by electric chair on March 20, 1933. He was just a bricklayer by occupation and was said to have suffered from mental delusions because of his ill physical health. There was no conspiracy plot found against the President-elect. However, the story is not that simple and it is alleged that Zangara was hired by Frank Nitti, who was an Italian American gangster and was the head of the Chicago Mob. His intention was to get killed the Chicago Mayor Cermak and this is exactly what happened. Nitti wanted Cermak to die because the latter had connections with the underworld rivals of the Chicago Mob and wanted to clean off Nitti.