Premise: Brutus de Villeroi (1794–1874) was a French engineer of the 19th century, born Brutus Amédée Villeroi (he added the aristocratic "de" in his later years) in the city of Tours and soon moved to Nantes, who developed some of the first operational submarines, and the first submarine of the United States Navy, the Alligator in 1862.
Hypothesis: Brutus de Villeroi was less than 50 years old when he died