The crimes of serial killers are always disturbing but teenage serial killers bring another level of terror. Its almost unfathomable to imagine someone who hasnt even graduated from high school plotting out heinous murders, but thats exactly what these adolescents did.Some of them came from turbulent households and faced abuse from a young age, while others were bullied at school and decided to take their anger out on people even more helpless than themselves. Whatever the case, these teen killers left a path of grisly destruction in their wake.Mary Bell was just 10 years old when she killed for the first time. Harvey Robinson became the youngest American serial killer ever sentenced to death at age 19. And Elmer Wayne Henley Jr. was the accomplice to an even more prolific killer. Their victims ranged from toddlers to the elderly and from innocent bystanders to fellow murderers.Below, go inside the chilling stories of nine teenage serial killers and the circumstances that led them to murder.Mary Bell, The 10-Year-Old Who Killed Two ToddlersWikimedia CommonsMary Bell murdered two toddlers in 1968.In 1968, a young girl named Mary Bell was convicted of two murders that shocked her native Newcastle, England. The day before her 11th birthday, she had lured a four-year-old boy named Martin Brown into an abandoned house and strangled him with her own hands. It must have taken a long time, because she wasnt strong enough to even leave marks on the boys throat. Thus, the cause of death couldnt be established at first.The following day, Mary and her 13-year-old friend, Norma Bell (no relation), broke into a local nursery school. They didnt take anything of value but they did leave a note confessing to the murder. It read: WE did murder martain brown fkof you bastard. At first, the police didnt take the note seriously. However, two months later, another young boy turned up dead in the same neighborhood. Three-year-old Brian Howe was found in a field on July 31, 1968. His hair was cut, his penis had been mutilated, and a large letter M was carved into his abdomen. The scissors used to cut into Howes body were discovered nearby, but investigators determined that his cause of death was strangulation, just like Martin Browns. The police questioned local children and learned that Brian had been seen with Mary Bell just before he disappeared. When detectives interrogated Mary, she denied any wrongdoing. However, she slipped up when she claimed that shed spotted Brian with an older boy the day of his murder. She stated that the boy was carrying scissors but only the police knew about the scissors found at the crime scene at the time.Public DomainWhitehouse Road, where Mary Bell lived, pictured here in 1966.Norma Bell was also questioned, and she blamed Mary for Brians murder. In turn, Mary said that Norma had killed the little boy. The case went to trial that December, and while Norma was acquitted, Mary was convicted of the manslaughter of both Martin Brown and Brian Howe. She wasnt found guilty of murder due to diminished responsibility because of her age. But why would a preteen kill two young boys? In 1998, author Gitta Sereny published an account of the crimes based on interviews with Mary Bell herself. According to a report in The New York Times the year after the books release, Marys mother was a sex worker who had tried to kill her daughter on several occasions and even allowed her clients to sexually abuse Mary. Reflecting on her crimes to Sereny, Bell stated, I didnt know I had intended for them to be dead dead forever. Dead for me then wasnt forever.Mary Bell spent 12 years behind bars and was released in 1980 at age 23. She was granted anonymity and today lives under a pseudonym, as does her daughter. The post Im Not Real Sorry For What I Did: 9 Teenage Serial Killers And The Chilling Crimes They Committed appeared first on All That's Interesting.