Factual error: When Vincent enters the nightclub, you can see that a woman is walking through the metal detector, but the security guard is scanning her with a hand-held wand at the same time. This is totally unnecessary. The hand-held should be used only if the walk-through is triggered. (00:43:50)
Factual error: In the shootout scene, De Niro loads the injured Kilmer into a stolen Ford wagon, drives backward pushing yet another unoccupied car out of the parking lot. Despite that second car being unoccupied in a parking lot, the car rolls backward (which it can't do in park or with a park brake applied), and after a few car lengths, the pushed car suddenly turns sharply (which doesn't happen with a locked column, which is standard equipment that self-activates when the ignition is shut off). Now, if the car were left running, in neutral, with no brake applied, everything that occurs would be possible. But the combination is very unlikely, especially right behind the car that a fleeing bank robber will choose to steal and ram into it. (01:52:15)
Factual error: As Al Pacino is catching up to Robert De Niro on the freeway he uses his walkie talkie to get an update on De Niro's location. He does not take his finger off of the talk button and therefore would not be able to hear the helicopter pilot's response.
Factual error: At the end of the movie, Pacino is chasing De Niro amongst the Navigational Aids at the airport. As a jet approaches, the approach lights are turned up to full brightness. Full bright is only used during decreased visibility (not the case in this scene).
Answer: Waingro helped Van Zandt track down Trejo. Waingro then tortured Trejo and threatened his family if he didn't give up McCauley. With his back to the wall, Trejo gave Waingro and Hugh Benny the details of the bank heist, but Waingro killed Trejo's family anyway and beat Trejo almost to death. Benny then gives the tip to the police on Van Zandt's order.
BaconIsMyBFF
I wonder how Trejo was tracked, I don't remember his name being revealed during Waingro's time with the crew, or any other information.
Well, we never see the crew prior to their first heist. Trejo could have given Waingro his name during the planning of that heist.
BaconIsMyBFF
Waingro met this crew only once. How would he know who Trejo is or where he lives? Right before the heist, Trejo is asked to mislead police away from the heist.