Karl Arnold

"Wives wither... children perish... but me? I'm an excellent father."

Karl Arnold, Sr., a.k.a. "The Fox", is a prolific serial killer and family annihilator who first appeared in Season One of Criminal Minds.

Background
Karl worked as a family psychiatrist. It was revealed in "Outfoxed" that he was abused (and possibly molested) by his father and, over time, developed an intense self-hatred. At some point in his life, he married a woman named Fay, with whom he had two children, Karl Jr. and Sarah. He was very controlling, bordering on obsessive-compulsive, which resulted in a divorce about five years prior to "The Fox" in which Fay won full custody of their children. After that, Karl took some time off from his job, became unfocused, and started drinking heavily. Prior to "The Fox", he infiltrated the homes of families he was treating, took them hostage, and pretended to be their father before killing them.

The Fox
After Karl kills eight families, the BAU is called in to investigate, but they only believed they were investigating the deaths of two families, the Millers and the Crawfords, as the rest of the families' deaths were apparently unconnected. After tracking him down, Morgan and Gideon followed him into the basement of the Dunkens's house, where he used the Dunkens baby as leverage. Karl eventually handed over the baby before making an attempt to escape, but Morgan, an expert in martial arts and a judo black-belt got the better of him and threatened to break his neck if he even moved. Back at the BAU headquarters, the team tricked him into confessing by switching the places of two crime scene photos on a board. Since Karl couldn't stand anything being out of place, he had an outburst, accidentally confessing to having detailed knowledge of the murders. When Hotch searched his office, he found a box containing eight wedding rings, including those of the Miller and Crawford families.

Outfoxed
"Once I killed the children, it always amazed me how little the father fought the inevitable." "Which was that?" "Dying."

According to Karl, after his murders became public knowledge, he gained a number of fans, some of which even made a website dedicated to him. In the episode "Outfoxed", a spree killer targeting entire families is active in Hampton, Virginia. Hotch and Prentiss interview Karl at Red Onion State Prison, where he assists in their investigation after receiving envelopes containing newspaper clippings about the murders which appear to have been mailed by the killer. During this, he comments on Prentiss in inappropriate ways, causing Hotch to agree to have Prentiss interrogate him alone, which she is later of herself by for "flirting" with Karl to get info. At the end of the episode, Karl reveals that one of them also contained a newspaper article about George Foyet's attack on Hotch, signed with his signature Eye of Providence, as a way to announce that he was returning. As Hotch left, Karl laughed in delight at his despair.

A year later, while investigating another spree killer specifically targeting families, Prentiss brings up Karl as an example of a family annihilator.

Profile
Organized killers are typically skilled workers with above-average intelligence, a high birth status and are often male. He is both socially and sexually confident. He does extensive research about his victims and takes a lot of time to make up a good plan before killing them. He keeps all this information in a book or journal, ensuring that nothing's left to chance, and never leaves anything out of place. When asked why Karl killed the way he did, he replied "to show what happens when the head of household isn't strong". He also appeared to be obsessive-compulsively neat, as revealed by his well-organized office. According to Prentiss in "Outfoxed", Karl was sexually motivated and killed the fathers as surrogates for his own father and himself.

Modus Operandi
"...And I watched them, for a number of days, always at night. Saw how they lived, how they loved. I would keep them apart, until the last night, until the last supper. Then I would bring them, one by one, down to the basement, the youngest first, father last."

Karl murdered families he viewed as dysfunctional. He would strike his victims when they were supposed to be on vacation, ensuring that nobody was surprised to not see them. He bypassed the alarms and killed the family's dog if they had one. He would separate the family members under death threats and keep them apart for days, until he took them to the house basement and killed them by slashing the children and wife, starting with the youngest, brought down the father and staged his suicide by gunshot. During those days, he would terrorize them, make the children draw paintings (a technique used by family therapists to assess the family's situation). On the final day, he would bring them together for one final dinner. After killing them, he would take the wedding rings as trophies. It was revealed in "Outfoxed" that he also physically abused the children and engaged in sexual acts with the girls, though that wasn't said in "The Fox".

Known Victims

 * Three unnamed men or families killed prior to The Fox
 * The Kegan family
 * The Ness family
 * The Linford family
 * The Miller family
 * The unnamed stepfather
 * Reese Miller
 * Ty Miller
 * Reese's unnamed daughter
 * The Crawford family
 * Christopher Crawford
 * Allison Crawford
 * Sam Crawford
 * Emily Crawford
 * The attack at the Dunkens home:
 * The Dunkens family
 * Harry Dunkens
 * Robin Dunkens
 * Jackie Dunkens
 * The unnamed baby son
 * Derek Morgan

Appearances

 * Season One
 * The Fox
 * Season Five
 * Outfoxed
 * 100
 * Season Six
 * Safe Haven