Visible crew/equipment: When Captain Navarro and the team are at the elderly victim's home, after Elle finds the bead from a necklace, in the next wide shot of Morgan, Navarro, Gideon, and Hotchner, the red T-mark can be seen on the floor in front of Gideon.
Factual error: In this episode Gideon mentions Andrei Chikatilo, and says that he lived in Ukraine (and that this is why he remained uncaught for so long). While Chikatilo was born in Ukraine, he lived in Russia for most of his life, and all of his murders happened here. An expert like Gideon should not make this kind of mistake.
Continuity mistake: In the elderly victim's home, when Gideon is going through the dresser drawers he finds the small frame with the picture of her son, and there is a blue frame lying in the drawer, but in the next shot that blue frame is lying on the dresser even though he never touched it.
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 her 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