Visible crew/equipment: When Neil (De Niro) breaks into Van Zant's apartment and shoots him, watch as Van Zandt flies backward. You can see a wire running up through the bottom of his sweat pants.
Continuity mistake: When De Niro confronts Ashley Judd in her motel room, he knocks all but a few hangers off of the metal coatrack. While the camera goes back and forth while they argue, the remaining hangers disappear and reappear several times.
Visible crew/equipment: In the drive-in shootout scene, the camera and crew are visible in the rear view mirror in the cab of the white Dodge pickup fleeing De Niro and Kilmer.
Revealing mistake: In the scene when Pacino leaves the police station to go to his hotel for a shower, the camera is pointing up a tree lined street. Watch the pedestrians - they are all standing still until the car comes into view then someone obviously shouts action and they all start walking.
Visible crew/equipment: In the scene where Hanna and Casals break into Hugh Benny's apartment, when they break down the door it can be seen that a stuntman is filling in for Pacino.
Continuity mistake: When Neil sets off the fire alarm in Waingro's hotel, there is a little red sign above the fire alarm when shown from far away. When it shows his hand up close pulling the alarm, the red sign is gone.
Continuity mistake: At the end of the movie, after the shootout between De Niro and Al Pacino, De Niro's character is dying. Al Pacino's character holds his hand and you can see, in different shots, the blood on his shirt changes.
Continuity mistake: In the shootout scene when they drive away in the car, De Niro is seen in slow motion as he realises there are cops in front of them as well as behind. He raises his weapon and fires, knocking the rear-view mirror off the window. In the shot directly after he is seen still firing his weapon and the mirror falls off the window again.
Continuity mistake: The ambulance that de Niro steals at the start of the film has a red stripe on the sides, but for the remainder of the film there is also a silver 'L'-shaped graphic as well.
Continuity mistake: When they torch the ambulance, you can see a dealership emblem that says "LEADER" right above the Chevrolet emblem on the back door of the ambulance. It is visible right after Chris puts the bomb in. In all other shots with the ambulance, this emblem isn't there. Obviously the "LEADER" ambulance is a "fake" that they used just to burn and destroy.
Visible crew/equipment: When Michael Cheritto comes out from the bank just before the shootout scene and gets on the car, a cameraman and a crew member on his right side opening the car door are reflected on the windows.
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.