In July 1935, two months prior to his death, Long claimed that he had uncovered a plot to assassinate him, which had been discussed in a meeting at New Orleanss DeSoto Hotel. According to Long, four U.S. representatives, Mayor Walmsley, and former governors Parker and Sanders had been present. Long read what he claimed was a transcript of a recording of this meeting on the floor of the Senate.
Long called for a third special session of the Louisiana State Legislature to begin in September 1935, and he traveled from Washington to Baton Rouge to oversee its progress. Although accounts of the September 8, 1935 murder differ, most believe that Long was shot once or twice by medical doctor Carl Austin Weiss in the Capitol building at Baton Rouge. Weiss was immediately shot sixty-one times by Long's bodyguards and police on the scene. The 28-year-old Dr. Weiss was the son-in-law of Judge Benjamin Henry Pavy. According to Mrs. Ida Catherine Pavy Boudreaux of Opelousas, Pavy's only surviving child, her father had been gerrymandered out of his Sixteenth Judicial District because of his opposition to Long.
Shortly after being shot, the expiring Long reportedly said, "I wonder why he shot me." Long died two days later of internal bleeding, following Dr. Arthur Vidrine's attempt to close the wounds.
An alternative theory suggests that Weiss was unarmed and had punched Long, not shot him. Instead, Senator Long was struck by a stray bullet from his bodyguards, who shot Weiss because they mistakenly believed that Weiss was going to shoot Long. Former Louisiana state police superintendent Francis Grevemberg supports this view of the shooting.