Leon was a worker at the Raptor Research Arena. He fell into the pen with the Velociraptors while attempting to retrieve an escaped piglet. As Blue, Delta, Charlie and Echo closed in around him, however, Owen Grady ran inside and was able to make the four dinosaurs back down, as Barry dragged Leon out of the pen to safety. owen warned the young man to be more careful in the future.
Later, during Vic Hoskins' plan to use Owen's raptor squad to hunt down ( kill) the escaped tyrannosaurus rex, Leon was the one who opened the doors, setting the raptors free to pursue the other predator.
Leon's fate after this is unknown. Although the raptors are seen attacking several Jurassic World employees after the tyrannosaurus persuades them to turn against the humans, Leon doesn't appear to have been among their victims and it is possible he was evacuated off of the island to safety.