Revealing mistake: When Hotch and Spencer are interrogating Eddie, Spencer shows him the three photos of the people he has killed. Eddie makes a gesture as if to speak and points at Spencer, at which point we see a shot of Spencer and he very obviously glances into the camera.
Revealing mistake: When the suspect is first put in handcuffs at the house, it's clear to see he is just holding the one cuff rather than wearing it. (00:27:50)
Revealing mistake: We see the jet at the end, and the shot is flipped. Note the serial number on the plane's engine. (00:38:05)
Revealing mistake: Just as Vincent gets tazered, you can see protective padding that he is wearing. This is not to be confused with his jacket. (00:25:10)
Answer: "The Boogeyman", s02e06. Spoiler alert: The kid is Jeffrey Charles and at that point he had already killed 3 other kids. Jefferey basically hated and resented other kids after his mother abandoned him and his father spent a lot of time with other children because of his job. Jeffery would lure kids Into the Woods and then beat them to death with his bat just because of hate, no particular "reason." The scene you're describing, Jefferey agrees to walk Tracy home when her "buddy" leaves her (at this point the FBI announced there's a serial killer on the loose and kids should walk with a buddy). Jeffrey gets mad at Tracy for walking too slow and for complaining, and he takes a swing at her, causing her to flee Into the Woods and have Jeffery chase her.
Bishop73