- "THEY'RE EVERYWHERE!!"
Before Jurassic Park
It was likely that Vargas was a veteran of one of the wars fought during the cold war, most likely the Korean or Vietnam war (Vargas shouts many things like "where are you hiding, in the trees?" and "we're sitting ducks out here in the beach." although he is inside a building. when asked about the helicopter crash, he says "the commies were trying to take off.") It is probable that PTSD from his time in combat led him to be exceptionally violent in his delirious state.
Isla Nublar Incident
After getting bitten by a Troodon, he went into a delirium and killed his two comrades, Garza and the pilot Linares, and shot down the chopper. Billy Yoder and Oscar Morales later find the dead comrades and the wrecked chopper. They proceed inside the Visitor Center, having heard gunshots and Vargas yelling insanely, which is infested by the Troodon and the Compys. After hearing more gunshots, Oscar volunteers to stop Vargas from causing more trouble, while Yoder goes to the Control Room and uses the security camera system to find him. After Oscar scares some of the dinosaurs away with his gun, Vargas reveals himself and tries to shoot Oscar, but misses and later uses a flash grenade against him. But with Yoder revealing his position, Oscar manages to disarm Vargas by shooting him in the shoulder.
While the group were in another room, a Troodon's head came out of a hole in a door and bit Vargas' foot. As Vargas screams in pain, he collapses and the Troodon drags him into the other room, devouring him.
Later in the game Billy Yoder yells and tries to kill Dr. Sorkin for unleashing the Troodons leading to Vargas' death, along with Daniel Cafaro and Oscar Morales even though Oscar was killed by Velociraptors, not Troodon.