Audio problem: When Reid and Morgan are walking up the stairs to the first victim's apartment they are talking, but their mouths aren't moving. (00:06:05)
Audio problem: Garcia is typing on a flat, foldable rubber keyboard but the keys' sound is loud like from a plastic keyboard. The rubber keyboard shouldn't make noise. (00:39:00)
Won't Get Fooled Again - S1-E3
Audio problem: The video game Penelope is playing is supposed to be Tetris, but the sound effects are from the Atari 2600 version of Pac-Man. You can hear Pac-Man die four times during the scene. (00:12:20)
Audio problem: When Tabitha gets home, she takes her boots off and as she walks into the kitchen we hear the soft, padded sound of bare feet; when she closes the fridge and walks to the window, her footsteps indicate she has her boots on again.
Audio problem: As Scott McCarty is shot there is no sound of a shot being fired, suggesting a silencer, however as the assailant's rifle is pulled inside the car you can see that the weapon has no silencer.
Audio problem: When Garcia is talking about the cross-examination she's done and how she should be praised for how quickly she'd done it, she crosses the room away from the computers (and the webcam she's shown through) to a bulletin board. While she's walking away, her voice gets fainter, and then becomes louder again when she returns, as though she were getting further and then closer again to a microphone. However, she is wearing a headset with a microphone - the volume wouldn't have changed. (00:13:15)
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