The Caller - S9-E10
Continuity mistake: At the beginning, a St Louis couple has reported their son missing. At the FBI briefing, the agents are told that the boy's mother tucked him in at 10:00pm. A few minutes later, we hear the radio call over footage of police at the home, and the dispatcher says "Last seen at 2100." That's 9:00pm, not 10:00pm. (00:03:00 - 00:05:00)
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