Walter Kern

"I need to do this. I can't stop it."

Walter Kern, a.k.a. "The Keystone Killer", is a serial killer who appeared in Season One of Criminal Minds.

History
Walter started killing in Philadelphia in 1986 and garnered the nickname of The Keystone Killer. It is mentioned that he served in the Reserve Officers' Training Corps in high school, got a degree in criminology from Villanova at some point, and served in the U.S. Air Force for four years. He had been a county worker, a claims adjuster, and, during his initial serial killing phase, installed home alarms; all jobs gave him access to peoples' homes. At some point, he worked together with Scott Harbin, a fetish burglar who was suspected of being the Keystone Killer. He apparently selected his victims before he started killing them; all were brunette women in their twenties at the time. When Walter was about to kill Carla Bromwell in 1988, he was involved in a car accident, which severely damaged his spinal cord. He eventually recovered but lost a lot of strength in his right side. During his recovery period, he apparently suffered from depression, which went away when he started killing again. At some point in his life, he got married.

Starting with Carla Bromwell, whom he targeted because he was compelled to finish the job with her, he began killing again in 2006, his M.O. having been drastically changed as a result of the car accident. After killing Carla Bromwell in "Unfinished Business", he sent a letter to Max Ryan, the former profiler who chased him in the 80s and went on to write a book about the Keystone Killer. After investigating Carla Bromwell's murder and being led to the suspected Keystone Killer, Scott Harbin (a puzzle sent along with the letter provided the clue), Max, who was temporarily employed as a consultant, and the BAU realized that Walter changed his M.O. because he had to. Narrowing the list of suspects down, they found Walter and arrested him just as he was about to kill another woman named Sylvia Gooden, whom he had been stalking since the 80s. As he was arrested by Morgan, Walter taunted Max. He would go on to be specifically mentioned in Pay It Forward as an example of serial killers who go dormant for long periods of time or completely quit.

Profile
Walter has been described by Ryan as a narcissistic sociopath who kills because he wants to rather than a psychopath who kills because he has a compulsion to do so. He was apparently a perfectionist, having to complete the series of killings he started. Max's original profile was of someone in his late 20s (in "Unfinished Business", late 40s). He appeared to have a possible military background, would drive a late-model American-made sedan, and has presumably been living in Philadelphia all his life. He would possibly hold some position of authority at work.

As the killer's puzzles contained references to even the smallest details of the crime scene, it meant he was probably taking pictures of the places he killed in, using the photographs to relive the murders. The Keystone Killer's change in MO, which included blitzing his victims, meant he may have been partially incapacitated in some way, either due to a stroke, or more likely, an injury.

Modus Operandi
When Walter killed during the 80s, he used his various occupations to gain access to his victims' homes without force and also apparently stalked his victims for some time prior to the kill. He then tied them up, using an intricate knot as part of his signature, and strangled them with rope. When he returned, he had lost a lot of strength in the right side of his body due to the car accident and had to use flex cuffs, which he forced the victims to put on themselves at gunpoint, pistol-whipping them to incapacitate them. He then placed a plastic bag over their heads, suffocating them. He would write taunting letters to the police, like Son of Sam and the Zodiac Killer, as well as word search puzzles which contained key words of the crime scenes. He also took photos of his victims, before and after they were killed, developed them himself, and then collected them in a scrap book. He also took their driver's licenses as trophies.

Real-Life Comparisons
Walter has several similarities to the Zodiac Killer and Dennis Rader, the BTK Killer. Like him and the Zodiac, he writes taunting letters containing some sort of puzzle (Zodiac sent ciphers; Walter and BTK sent word search puzzles) to the police. Like BTK, Walter worked as an alarm installer until 1988 and was in the U.S. Air Force for some time. Also, they both strangled their victims, or at least most of them, and stopped killing in the 80s only to return in the present.

Known Victims

 * The 1986-1987 killings:
 * Unspecified dates:
 * Six unnamed victims
 * Unspecified date 1987: Amy Jennings
 * Unspecified date in 1988: Carla Bromwell
 * 2006:
 * February 27: Carla Bromwell
 * March 1: Sylvia Gooden

Appearances

 * Season One
 * Unfinished Business
 * Season Four
 * "Zoe's Reprise"
 * Season Eight
 * Pay It Forward