Jonny Grusing was a Special Agent (SA) with the FBI’s Denver Division from 1996 to 2021. For 23 years of his career, he worked violent crime matters to include missing persons, serial killers, federal jurisdiction homicides and mass attacks. From 2008 until his retirement, he served as the Behavioral Analysis Unit (BAU) Coordinator for the division. SA Grusing received extensive training from the profiling unit during these years and employed that training in addressing the serious violent crime cases in Colorado. From 2013 through the present, he has taught hundreds of seminars on profiling serial killers and preventing mass attacks using the sound BAU principles. He is now Director of Security for the Douglas County School District in Colorado.

From 2006 to 2021, SA Grusing was the case agent assigned by the FBI to investigate the homicides committed by serial killer Scott Kimball. He worked with local and federal investigators to recover Kimball's victims in various states and formed a long-term relationship with the killer in efforts to reveal the extent of Kimball's heinous crimes.