BTK was a Cub Scout leader and used a false story as an alarm repairman to gain entry to one of his victim’s houses.

Rader used an ADT hard-hat and a Southwestern Bell manual to pose as a technician for the telephone company.[117] Rader first gained entry into Wegerle’s neighbor’s house, and pretended to do telephone work, before leaving and knocking on Wegerle’s door, doing so to make Wegerle less suspicious.

Fun fact: his son served on the naval base in New London at the same time as me. Not on the same submarine, but same waterfront a few piers down. Ran into him a few times.

Dennis Rader was a serial killer known as BTK (an acronym for Bind, Torture, Kill). His day job was installing security systems for ADT. Many of the people he installed security systems for were specifically concerned about BTK. He was also the leader of a Cub Scout troop.

Assuming this: https://en.wikipedia.org/wiki/Dennis_Rader