Easter egg: In the special features on Disc 6, select "The Making of Criminal Minds" and press up on your remote. A small "x" should become highlighted. Select it to view the presentation of the "First Annual Gooby Awards", a collection of fictional awards for the cast and crew.
Easter egg: In the special features on Disc 6, go down to "Inside Quantico and the Criminal Mind", and press right on your control; this should highlight the image of a gun. Select it to view a short tour of the CM offices and set with Edward Allen Bernero's assistant Rosalie.
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