Revealing mistake: When the (imposter) female security guard was lying on the floor with her head slightly raised and shot herself, the gun was about parallel to the floor; the blood splatter should not end up primarily mid-way up the wall like it did. The floor-level view of the dead guard shows a reduced-size wall so that the blood splatter looks much closer to the floor than it was. Also, at least some blood should be visible on the guard's temple but none was. (00:35:40)
Continuity mistake: The position of the dead (imposter) security guard's head over the barbell changes. When Gus says, "Jesus, he's dead", the security guard's neck is over the barbell rail, the top of his head is touching the floor, and his face is toward the front of the screen. When the camera goes to the opposite side of the dead guard, his head and neck are raised (and apparently no longer being supported by the barbell - or anything else). (00:28:28)
Revealing mistake: When the (imposter) security guard threw the barbell and smashed the mirror, the mirror appeared to shatter just before impact. (00:28:05)
Other mistake: Alpha was standing at an angle to the senator when he shot him in the forehead, but the bullet hole was not angled as would be expected. Alpha was also holding his gun slightly upward when aiming at the senator's forehead, but the majority of the (odd-shaped) blood splatter behind him was near the back of his neck instead of higher. All blood splatter went behind the senator, but some should have been in front. (00:21:05)
Revealing mistake: After the kids take their seats at the game, the people behind them change, indicating the use of a green screen. (00:13:00)