Warren was last seen on the St. Lawrence River in Alexandria Bay, New York on May 26, 1990. He was riding in a 22-foot speedboat with three others. They were going too fast and the boat struck an eight-ton buoy about 25 miles north of Watertown between 1:30 and 2:00 a.m. The boat was completely destroyed in the collision. Two of the other passengers in the boat were rescued. The remaining passenger, Mary Beth Caruso, drowned, and Warren disappeared. He is presumed to have drowned, although his body has never been located. He lived in Salina, New York and worked as an electrician at the time of his disappearance.