"Helen...Helen, you were destined to find me. We were...we were destined to find each other..."
Little information is revealed about Kohler's early life, other than he became a prison shuttle driver. As a result of his job, Kohler came to know Helen Garrett, who visited her husband, a notorious serial killer named Rodney Garrett, daily at Gunter State Prison. The two became acquainted and Kohler eventually fell in love with her. Coming to view Garrett as an enemy, Kohler twice arranged the shanking of Garrett to get him out of the way, but both occurrences failed when Garrett gained the upper hand and killed his assailants. Both shankings happened on the day after Garrett's scheduled executions were postponed. Learning that Helen was bald due to a surgery for a brain tumor, Kohler, at this point deluded, decided to start a mission to give her "the perfect wig".
On the day that Garrett is scheduled for execution, he holds Cara Smith captive in her home and waits until a local news network announces Garrett's execution. He then murders her minutes later, at 6:30 a.m., and cuts off several strands of her hair, taking them and some flowers along with him. He also intentionally allows the body to be easily found as a taunt to the authorities. Six hours later, around noontime, Kohler attacks Jodie Armstrong, also cutting off strands of her hair and taking them with him. Another six hours later, he murders Karla Demshure and takes strands of her hair too. The BAU realize that he is killing every six hours and help local authorities urge the community to be on alert. A curfew is resultantly placed on the town. Near midnight, Kohler breaks into the home of Emily Sisk and goes to her bedroom, thinking she is sleeping inside, but doesn't find her. Minutes later, Emily and her boyfriend, Gary Hazlett, arrive and the latter goes inside to get some beer while Emily talks on the phone with her mother. Gary is ambushed by Kohler, who beats him into submission before being spotted by Emily, who flees with Kohler in pursuit. He catches up with Emily and tries to kill her, but the struggle awakens a neighbor and Kohler is forced to abduct her instead.
Successfully fleeing, he then kills Emily, by stabbing her repeatedly to death instead of once through the heart. He then removes her scalp, and takes a huge risk by dumping the corpse near Emily's house while the BAU and police are still present. The next day, 6:00 a.m. has passed without a single murder, for Kohler has attended to his job. He carries out the final phase of his plan, abducting Helen Garrett when she is the only passenger on the prison shuttle and taking her to his house. There, he has her wear the wig he designed for her and prepares to have dinner with her when the BAU, having realized he was the unsub, burst into the room, forcing Kohler to hold Helen at knifepoint with one of his icepicks. He refuses to release Helen, forcing Hotch to non-fatally shoot him, allowing Helen to escape. Kohler eyes the icepick he dropped but is arrested before he can grab it. By the end of the episode, he is visited by Helen, who had suddenly come to like him. She reads him a quote that Kohler states he hasn't heard of before, which is the same quote Garrett used before his execution, having learned it from several fan-letters sent to him. However, as Kohler, who had been initially presumed to be a "fan" of Garrett's due to his copycat murders and therefore would've been eligible to write those letters, didn't hear of the quote while Helen did, this implies that it was she who had written the letters to Garrett and not Kohler.
Kohler copied Garrett's M.O., with some differences. After forcing his way into their homes, he tied his victims, who were young, long-haired, blonde Caucasian women, to their bed frames with duct tape. His signature was cutting their hair with scissors (or, in the case of Karla Demshure, shaved) to make them more similar to Garrett's victims, who had been short-haired (he took the hairs with him afterwards). He would then gag them and kill them by stabbing them straight through the heart with an icepick that would be left there.
Unlike Garrett, who committed his murders over the course of two years, Kohler attacked his victims consecutively in a single day, and, for unknown reasons, around times whose numbers are divisible by six, such as 6:00, noontime, and midnight. He also picked out the locations of the victims' residences so their outline formed a heart on a map, with Helen's home located at the center of it, as it was meant for her. Also, Garrett targeted high-risk victims such as prostitutes, drug addicts, and runaways, while Kohler targeted low-risk victims. Kohler was also much more careful not to leave behind evidence, dressing up in a full-body suit with gloves. Later on in his killings, Kohler began abducting his victims and also departed from his six-hour-long cooling-off period due to the heightened alert in the community from his murders.
As mentioned earlier, Kohler took the hairs he cut from his victims afterward. He would use these hairs to fashion a makeshift wig for Helen. To complete the wig, he removed most of Emily Sisk's scalp after killing her and used it in said wig. Also, he would take several other items, specifically ones that were typically associated with a romantic party, such as flowers and a glass of wine, from the crime scenes. He would use these items to set up a "dinner" for him and Helen.
The unsub is a 30-40 year old white male who is strong enough to subdue physically fit young women with minimum resistance. He is forensically sophisticated, conscious of evidence left behind, targets his victims in advance, and leaves no trail. He is also confident, since he is taunting the authorities by leaving the bodies of his victims behind in plain sight and allowing for the bodies to be found quickly after their deaths. Because of his ability to plan and flawlessly execute his attacks, he is also able to hold down a job, though it is probably a menial and unfulfilling one. The victims being young, blond, and pretty may, to the unsub, represent a societal standard of perfection unattainable to him. The unsub's way of cutting their hair and taking them with him may be a way to degrade them, as they are unattainable, or might be an intention to take a part of them with him. He kills his victims in six-hour increments, essentially time-stamping his victims.
It is difficult to determine whether Kohler is a serial or spree killer. While he targeted specific victims and planned out the murders beforehand, it should be noted that he attacked several people in over 24 hours.
- May 25, 2008: Rodney Garrett (attempted; hired an inmate to shank him, but the inmate was killed by Garrett)
- November 15, 2010: Rodney Garrett (attempted to kill again with the above means; the inmate was killed by Garrett)
- April 29:
- Cara Smith (killed at 6:30 a.m., minutes after Garrett's execution)
- Jodie Armstrong (killed at around noontime)
- Karla Demshure (killed at around 6:00 p.m.; shaved her hair off post-mortem)
- Gary Hazlett (Emily Sisk's boyfriend; incidental; assaulted while abducting Emily and presumably intended to kill)
- April 29-30: Emily Sisk (abducted at around midnight, stabbed repeatedly in the torso, removed her entire scalp post-mortem, and dumped her body by her home)
- April 30: Helen Garrett (Garrett's wife; abducted and later held at knifepoint with an icepick; was rescued)
- April 29:
- Kohler has some similarities to copycat serial killer Chloe Kelcher, who also partially copied the M.O. of an executed serial killer who targeted women, attacked them in their homes, and used a sharp instrument in his killings (Garrett used icepicks to kill his, Cortland stabbed his with a screwdriver post-mortem).