Warning: Graphic and disturbing content ahead including mentions of assault, rape, abuse, and murder.
1. The "Alphabet Killer," who is believed to be responsible for the sexual assault and killing of three girls between 1971 and 1973 in Rochester, New York. The victims all had names whose initials were the same letter: Carmen Colón, Wanda Walkowicz, and Michelle Maenza.
2. "Bible John," an unidentified serial killer who's believed to have murdered three women between 1968 and 1969 in Glasgow, Scotland. The killer was dubbed "Bible John" because, according to a witness, he would quote Bible scripture.
3. The "Stoneman," an unknown serial killer in India who murdered at least 26 people experiencing homelessness, while they were asleep, in the mid to late '80s. The moniker comes from the fact that the killer would crush the victims' heads with a large stone.
5. The "Doodler," a serial killer who is suspected of killing and/or assaulting as many as 14 men in San Francisco from January 1974 to September 1975 and was never caught. The moniker came from the fact that the Doodler would sketch his victims before stabbing them.
6. The "Butcher of Mons," an unidentified serial killer who is believed to have killed at least six women in or around Mons, Belgium between January 1996 and July 1997. The victims' bodies were dismembered with "anatomical expertise," and various body parts were left in "neatly tied" bags.
8. The "Monster of Florence," an Italian serial killer (or killers) active in the areas in and around Florence, Italy from 1968-1985. Their killings were so shocking they inspired the creation of the character Hannibal Lecter.
9. The "Phantom Killer," or "Phantom of Texarkana," an unidentified killer responsible for several unsolved serial murders and related violent crimes in and around Arkansas and Texas in 1946. The crimes were so shocking to the community that they would go on to inspire the 1976 film The Town that Dreaded Sundown.
10. The "Severed Leg Killer," an unidentified serial killer who murdered several people in Turkey from 2000 to 2001. The moniker was given because severed legs from the victims were found around different areas in Istanbul.
11. The "West Mesa Bone Collector," who is believed to be responsible for the murder of 11 women in Albuquerque, New Mexico. The victims' bodies were discovered in 2009, after having been buried in the desert.
12. The "Long Island Serial Killer," aka the "Gilgo Beach Killer" or the "Craigslist Ripper," a suspected serial killer who is thought to have murdered 10-18 people over a period of 20 years. The victims' bodies were found along the beach in Long Island, New York starting in 2010.
13. The "Oakland County Child Killer," aka the "Babysitter Killer," who was active in Oakland County, Michigan between 1976 and 1977. The unidentified perpetrator (or perpetrators) is responsible for kidnapping, holding captive, and then violently killing at least four children.
14. The "Belize Ripper," a serial killer active in Belize City from 1998 to 2000 responsible for the abduction, rape, and murder of several young girls. Although there was a major investigation, no one was ever convicted, and the murders remain unsolved.
15. The "Monster of Udine," an unidentified serial killer with at least four victims active in northeastern Italy from 1971-1989. All the victims were women, some sex workers, and were killed either by stabbing or strangulation. One victim even had an incision that was shaped in a kind of "S" formation.
16. The "Danilovsky Maniac," an unidentified serial killer suspected of killing at least seven people between 2004 and 2007 in the city of Cherepovets in Russia. The name comes from a location on Danilov Street where three of the victims' bodies were found.
17. The "Highway of Tears" killer (or killers), which refers to a 450-mile corridor of Highway 16 in British Columbia where many Indigenous women have gone missing and/or been murdered since at least 1986.
18. The "Axeman of New Orleans," a serial killer active in the New Orleans area from 1917 to 1919 who mainly targeted Italian immigrants and Italian-Americans and was never caught or identified.
19. The "North Kanto Serial Young Girl Kidnapping and Murder Case," involving five victims, all young girls between the ages of 4 and 8, that occurred between 1979 and 1996. None of the cases have been solved and no suspects arrested, either.
20. The "B1 Butcher," a serial killer who murdered at least five women in Namibia between 2005-2007 and was never identified. The killer was dubbed the "B1 Butcher" by the media because the victims' remains were found near the Namibian National Road B1.
21. The "Saw-Killer of Hanover," an unidentified serial killer in Germany who is believed to be responsible for murdering and dismembering at least six people in the 1970s and whose victims were not able to be identified, either.
22. The "Madman of the Route," an alleged serial killer who is believed to be responsible for the disappearance of at least 14 sex workers in Argentina from 1996 to 1999. The crimes were so gruesome that some of the victims were found mutilated with words written on their bodies.
23. The "Tyumen Maniac," an alleged serial killer in Russia who is thought to be responsible for the disappearance and possible murder of at least nine children since 1997.
24. The "Kigali Ripper," an unidentified serial killer (or killers) who murdered at least 15 sex workers, and possibly a witness, in Rwanda's capital city Kigali in 2012. All the victims were strangled and some mutilated.
25. The "Monster of the Mangones," an unidentified serial killer in Colombia active between the 1960s and 1970s who is believed to have kidnapped and killed over 30 adolescent boys in Cali.
26. The "Lisbon Ripper," an unidentified serial killer who murdered three sex workers between 1992 and 1993 in Lisbon, Portugal.
27. Finally, "Jack the Ripper," an unidentified serial killer active in 1888, who mainly targeted sex workers in impoverished areas of London.
If you or anyone you know has information on a missing person case, call local law enforcement first. You can also contact the National Center for Missing & Exploited Children at 1-800-843-5678 (THE-LOST) or visit the National Missing and Unidentified Persons System site for regional case assistance.