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The Devil I Knew: Unmasking a Serial Killer
The Devil I Unmasking a Serial Killer
“There’s a truth to everything I said, Jon. This is a puzzle. You have to figure it out.”
The puzzle included numerous murders across the western United States that serial killer Scott Kimball described in detail as we sat across from each other at a table in the Colorado Penitentiary in 2011. I had no doubt he had killed at least as many people as he claimed—considering how easily he had conned the FBI, and local police and judicial systems across many states while he was killing the four victims we knew about.
The Devil I Unmasking a Serial Killer is a true crime novel about the fifteen-year investigation by former FBI Special Agent Jonny Grusing into the homicides committed by Scott Kimball.
Kimball was an FBI informant in the early 2000s, reporting on multiple murder-for-hire cases while secretly making people disappear. Working closely with the FBI's profiling unit, a local detective, and state and federal prosecutors, Agent Grusing was the primary FBI investigator assigned to determine what had happened to the missing people. This team faced near-impossible tasks to prove homicide cases against Kimball and to locate his hidden victims. The book delves into the principles Agent Grusing learned from the FBI’s Behavioral Analysis Unit and how he applied those tactics as he interviewed and interacted with this highly intelligent, manipulative murderer. The story accounts for body recovery trips into the mountains of Colorado and outside of the state, includes extensive conversations with the victims’ families, explores other unsolved murders possibly tied to Kimball, and assesses the complete devastation this wolf in sheep's clothing left behind.
Jonny Grusing, a retired FBI Special Agent, spent 23 of his 25 years in the Bureau working on significant violent crime cases in Colorado, many of which are featured on true crime documentaries. Jonny combines much-needed humor with his incredibly harrowing account of tangling with the inhuman manipulation, deceit, and violence of this serial killer. This non-fiction novel will educate readers about the bare-knuckled challenges and the soul-draining experiences of facing off with a dangerous psychopath.
“A riveting inside account of Grusing’s exhaustive investigation and face-to-face dealings with the man who simply called himself . . . Hannibal.” —Robert Dean, Dateline, NBC
“Get ready for a roller coaster ride deep into the mind of pure evil.” —John Quinones, 20/20, ABC
“There’s a truth to everything I said, Jon. This is a puzzle. You have to figure it out.”
The puzzle included numerous murders across the western United States that serial killer Scott Kimball described in detail as we sat across from each other at a table in the Colorado Penitentiary in 2011. I had no doubt he had killed at least as many people as he claimed—considering how easily he had conned the FBI, and local police and judicial systems across many states while he was killing the four victims we knew about.
The Devil I Unmasking a Serial Killer is a true crime novel about the fifteen-year investigation by former FBI Special Agent Jonny Grusing into the homicides committed by Scott Kimball.
Kimball was an FBI informant in the early 2000s, reporting on multiple murder-for-hire cases while secretly making people disappear. Working closely with the FBI's profiling unit, a local detective, and state and federal prosecutors, Agent Grusing was the primary FBI investigator assigned to determine what had happened to the missing people. This team faced near-impossible tasks to prove homicide cases against Kimball and to locate his hidden victims. The book delves into the principles Agent Grusing learned from the FBI’s Behavioral Analysis Unit and how he applied those tactics as he interviewed and interacted with this highly intelligent, manipulative murderer. The story accounts for body recovery trips into the mountains of Colorado and outside of the state, includes extensive conversations with the victims’ families, explores other unsolved murders possibly tied to Kimball, and assesses the complete devastation this wolf in sheep's clothing left behind.
Jonny Grusing, a retired FBI Special Agent, spent 23 of his 25 years in the Bureau working on significant violent crime cases in Colorado, many of which are featured on true crime documentaries. Jonny combines much-needed humor with his incredibly harrowing account of tangling with the inhuman manipulation, deceit, and violence of this serial killer. This non-fiction novel will educate readers about the bare-knuckled challenges and the soul-draining experiences of facing off with a dangerous psychopath.
“A riveting inside account of Grusing’s exhaustive investigation and face-to-face dealings with the man who simply called himself . . . Hannibal.” —Robert Dean, Dateline, NBC
“Get ready for a roller coaster ride deep into the mind of pure evil.” —John Quinones, 20/20, ABC
360 pages, Hardcover
Published August 28, 2025
86 people are currently reading
167 people want to read
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Displaying 1 - 7 of 7 reviews
March 13, 2026
The Devil I Knew, written by former Colorado FBI agent, Jonny Grusing, outlines his complicated and at times, frustrating, investigation of Serial Killer, Scott Kimball. Kimball, while working as an FBI informant, was responsible for the murder and disappearance of several people from Colorado.
Being a Colorado native, this book intrigued me as I can recall several of Grusing's cases and have traveled to or through many of the investigative locations/towns myself. His book gave me insight into what I may have found as a normal everyday location and realizing that such unspeakable acts can be a part of a location's history. It was my relatable things like camping in the National Forest, driving through Rifle and Grand Junction or even just knowing where some of the referenced streets and areas of last seen or known locations of the victims were.
The author did a great job of presenting the facts and his understanding of the case. By the end of the book, I had a better understanding of Kimball and found myself truly baffled that people like him, such con-men, really function the way that they do- such arrogance and psychopathic behavior. And to think this man lived amongst my fellow Coloradoan neighbors.
Jonny Grusing was faced with such a mountain of investigation, he became responsible for cleaning up the failure of another FBI agent who had no business taking on the additional role of 'parole officer'. This aspect of our system with allowing dangerous people to become informants failed several victims. Could this have prevented some of these senseless murders- possibly!
What I found relatable and redeeming was that Grusing developed relationships with the families of Kimball's victims. He took control of the investigation, had empathy, care and concern and wanted to seek truth and justice for LeAnn, Jennifer, Kaysi, Uncle Terry and Cat. Referenced in his book are a few other investigations that I recalled, like Dateline's episode, Over the Edge, and of course one headline that stuck with me, the disappearance and murder of Jessica Ridgeway.
I would recommend this book, especially to those who are interested in gaining insight into investigations or characteristics of serial killers, being from Colorado is a bonus because this investigation truly encompassed a large portion of the state. I would hope that Jonny Grusing considers writing about some of his other investigations, he writes very well and makes the read very relatable.
Being a Colorado native, this book intrigued me as I can recall several of Grusing's cases and have traveled to or through many of the investigative locations/towns myself. His book gave me insight into what I may have found as a normal everyday location and realizing that such unspeakable acts can be a part of a location's history. It was my relatable things like camping in the National Forest, driving through Rifle and Grand Junction or even just knowing where some of the referenced streets and areas of last seen or known locations of the victims were.
The author did a great job of presenting the facts and his understanding of the case. By the end of the book, I had a better understanding of Kimball and found myself truly baffled that people like him, such con-men, really function the way that they do- such arrogance and psychopathic behavior. And to think this man lived amongst my fellow Coloradoan neighbors.
Jonny Grusing was faced with such a mountain of investigation, he became responsible for cleaning up the failure of another FBI agent who had no business taking on the additional role of 'parole officer'. This aspect of our system with allowing dangerous people to become informants failed several victims. Could this have prevented some of these senseless murders- possibly!
What I found relatable and redeeming was that Grusing developed relationships with the families of Kimball's victims. He took control of the investigation, had empathy, care and concern and wanted to seek truth and justice for LeAnn, Jennifer, Kaysi, Uncle Terry and Cat. Referenced in his book are a few other investigations that I recalled, like Dateline's episode, Over the Edge, and of course one headline that stuck with me, the disappearance and murder of Jessica Ridgeway.
I would recommend this book, especially to those who are interested in gaining insight into investigations or characteristics of serial killers, being from Colorado is a bonus because this investigation truly encompassed a large portion of the state. I would hope that Jonny Grusing considers writing about some of his other investigations, he writes very well and makes the read very relatable.
December 3, 2025
I was so excited to read this & it did not disappoint. I don’t know Jonny Gursing but have followed many of his cases. When I was 19/20 years old, a young female was found murdered (Cat) behind a small strip mall where I was working at the time. I was young & beautiful. The murder of Cat shook my parents to the core. So much so, I wasn’t allowed to work there anymore and my parents kept me as close as possible. I remember reading about how her hands looked as though they were surgically removed. I wasn’t into trials & investigations until many years later so I never really followed the case at the time.
A couple of years ago I had a dream about the young woman (Cat) they found behind my work. That day I spoke with a work colleague who grew up in the same area. She remembered it vaguely. Later that night I researched it a little to see if they ever caught the person. “F🤬🤬king Scott Kimball” name kept coming up in articles. I knew of Scott and seen some documentaries but really never dug into him until this past year. It wasn’t Scott that caught my interest in his case. It was Agent Gursing’s interrogations and knowledge that caught my interest.
This book was very well written and did an exceptional job of telling some of his victims stories, even uncle Terry’s.
My prayers go out to Bob & all the victims families ♥️.
Side note: I had a dream last night that Scott Kimball & Letecia Stauch were in an interview room & Gursing said “Take your best shot at them & believe nothing”. 😬😬 more like a nightmare.
A couple of years ago I had a dream about the young woman (Cat) they found behind my work. That day I spoke with a work colleague who grew up in the same area. She remembered it vaguely. Later that night I researched it a little to see if they ever caught the person. “F🤬🤬king Scott Kimball” name kept coming up in articles. I knew of Scott and seen some documentaries but really never dug into him until this past year. It wasn’t Scott that caught my interest in his case. It was Agent Gursing’s interrogations and knowledge that caught my interest.
This book was very well written and did an exceptional job of telling some of his victims stories, even uncle Terry’s.
My prayers go out to Bob & all the victims families ♥️.
Side note: I had a dream last night that Scott Kimball & Letecia Stauch were in an interview room & Gursing said “Take your best shot at them & believe nothing”. 😬😬 more like a nightmare.
March 19, 2026
And now, the whole story can be told
I have lived in the SW Denver Metro my entire life and initially read about this case in the local Westwood Magazine.
Mr. Grusing has written an insightful tale that give the reader a true understanding of this serial killer and the pain and destruction that he caused to the victims, their families and the law enforcement officers that fulfilled their duties to investigate his crimes.
I highly recommend this book!
I have lived in the SW Denver Metro my entire life and initially read about this case in the local Westwood Magazine.
Mr. Grusing has written an insightful tale that give the reader a true understanding of this serial killer and the pain and destruction that he caused to the victims, their families and the law enforcement officers that fulfilled their duties to investigate his crimes.
I highly recommend this book!
November 29, 2025
It was extremely interesting to read a book by someone you know. Jonny and his wife attended the church where we go, Jonny even teaching my son’s class for a bit. Though I’ve always known he was an FBI agent, I had no idea this LONG lasting case was something he was working on. I’m not sure I could have condensed it down and made it readable but I’m very glad he did!
February 23, 2026
This book was very good. The author does an excellent job of telling the stories of the victims and the killer. It is not your regular true crime book. It gave great insight to the minds of the sociopaths and psychopaths and that was the most disappointing part.
April 18, 2026
This story is truly unnerving and horrifying, but reading it through agent Grusing’s point of view is absolutely fascinating.
March 11, 2026
Well written book by a local CO retired FBI special agent. It delves into the mind and crimes of serial murderer and con man Scott Kimball. It was eerie reading about local places I frequent and recalling the billboards of missing people I had seen during the times of his crimes in Colorado. After meeting Mr. Grussing and reading this book, I would really be interested in reading more about the many others crimes he solved in the area.
Displaying 1 - 7 of 7 reviews