In the school cafeteria, Miles starts falling before the chair hits him.
When Rich puts the gun up to Lee's head in the parking garage, there's the sound of a hammer cocking, but the gun (a Glock) doesn't have a hammer. It's cocked by pulling the slide back.
After their struggle with Lee, Rich tells Laura to start the car; however, the car has been running the entire time, as evidenced by visible exhaust from the tailpipe throughout the scene.