After being tutored by Vice President John Adams, Jacob Jay traveled to France to defend the King of France. While there, he was killed while training with the French military under suspicious circumstances. The French official report stated that Mr. Jay was killed by an accident. However, historians generations later would later discover that Mr. Jay was murdered by fellow soldiers either because of gambling debts or his father's plot to assassinate President Washington. Some conspiracy theorists even claim (incorrectly) that La Fayette and other Frenchmen with an affinity for Washington arranged for the murder.
Jacob Jay has died on November 2, 1790. He was 30 years old. He has been buried in Cimetière de la Madeleine near Paris, France.