Criminal Minds Wiki

I couldn't have written this any better.

Peter Harper was a budding serial killer, stalker, and abductor who appeared in the Season Eight episode of Criminal Minds, "The Gathering".


Not much is known about Peter's background, aside from the fact he worked in an office. He harbored murderous fantasies for years and took to writing therapy led by serial killer Mark Jackson in an effort to curb them; he would base the stories he submitted on women's personal documentations as posted on blogs and social media. He also began stalking Tammy, a woman he encountered on social networks, who made him feel normal. Little did he know that the stories he submitted to Mark were used as a basis for his murders.

The Gathering[]

"Keep reading. You haven't gotten to the best part."

In the episode, Peter is first seen hallucinating about stabbing his boss's hand with a pair of scissors when she scolds him for not being attentive to work. Later, he goes to watch Tammy as she swims at a local community pool, and hallucinates about drowning her in the pool. She texts him, and he texts her back. The next day, he sees a news report about Mark's victims, and he becomes horrified when he deduces that Mark had killed them. He goes on to tear down a board full of photos of Mark's victims. The following night, he goes to the writing therapy group and submits a new story late to Mark. When Mark reads it, he stops halfway, shocked by its content, but Peter urges him to read on. When the meeting concludes, he confronts Mark about the killings, and Mark taunts him, saying he should be grateful that his stories were used by him as guidelines. Peter then tells Mark that he never included the tongue removal in his stories before beating him to death.

He then escapes, having been satisfied by his murder of Mark, and abducts Tammy from her home, taking her to the community pool and tying her up. There, he tells Tammy to convince him not to kill her. She tries to play along with his delusions, even accepting a kiss from him, but when she tells him to turn himself in and get help, Peter immediately shoves Tammy into the pool just as the BAU arrive and hold him at gunpoint. He quickly holds a knife against his throat, intending to kill himself. Reid puts down his gun and admits that there is no cure for Peter's murderous urges but that all he has to do to fight them is to try, while Morgan dives into the pool to rescue Tammy. Peter lowers the knife, but then he says that he appreciates Reid's honesty and immediately slashes his own throat. His lifeless body falls into the pool, while Morgan is able to revive Tammy.

Modus Operandi[]

Peter beat Mark Jackson to death with his bare hands in a fit of rage. When he attempted to kill Tammy, he abducted her and bound her arms and legs to a chair. He then pushed her into a swimming pool while she was still restrained to the chair, in an attempt to drown her as part of his fantasy.


The unsub is a male who did not hold back his rage towards Mark Jackson when he killed him. Mark's murder was personal and did not show same level of confidence that Mark showed when he killed his victims, which means it was his first murder and most likely not his last. It is believed he was a member of Mark's writing therapy group, and when he found out he was using his stories as the basis for his murders, he subsequently unraveled. He would have called the same organization Mark volunteered at multiple times on the days he worked there. Water seems to be extremely crucial to his fantasy of killing the woman he has been stalking, which means he will kill her in a location that is close and has water.

Known Victims[]

  • March 20, 2013:
    • Mark Jackson (his therapist)
    • Tammy (previously stalked for an unspecified amount of time; abducted, bound, and non-fatally drowned; was rescued)