The media reporting and the Discovery Documents are a little slippery when it comes to specificity about when exactly Kessinger contacted the cops [or who contacted whom first], and the precise time this happened.
It appears the first time Kessinger spoke to law enforcement was on August 15, the same day Watts confessed. It’s possible that Kessinger was contacted by phone first [prior to the discussion below on August 15], or that Kessinger herself contacted the cops by phone.
Although this interview was recorded, and despite many YouTube clips claiming to the be the “first interview” with Kessinger, her meeting with the FBI’s Mark Lehrer was her first one-on-one interview with law enforcement. Below is the audio of that first interview. Give it until 3:28 before the static “settles down”.