Returning to France he fell in with a scheme of Bernou's to establish a base at the mouth of the Rio Grande for the conquest of Mexico. To make it seem more feasible to the king he falsified geography, situating the Mississippi over 600 miles west of its true course. Given command of the expedition, he displayed incompetence and paranoia. That, and his earlier duplicity, caused him to land in February 1685 at Matagorda Bay [Texas] which he claimed to be an outlet of the Mississippi. Most of the expedition's supplies having been lost and the Indians alienated, starvation loomed. In April 1686 La Salle set off with 20 men to seek help at Fort St-Louis-des-Illinois. Dissension in his party and at the base resulted in desertion and murder, and finally in the assassination of La Salle. The wonder is that his men had not killed him long before.
A romantic hero to 19th-century historians, La Salle was in fact a victim of his own incapacities. His one claim to fame is his descent of the Mississippi, upon which French claims to Louisiana were to be based.