We all know stories about famous killers, but there are ones far more dangerous that we've never been told about
In 2011, while investigating the murder of "Shannan Gilbert", the police found a grave with 4 bodies. They then dated them back as late as 1996. Amongst the victims was a girl named Melissa. When her parents reported her missing, the police didn't take her seriously until her sister started receiving phone calls of someone saying "I killed Melissa"
When discharged from the army, Israel Keyes in 2011 went and dug up his "murder kit". He then choose a few people, killed them, and left the city. He was then caught in 2012 when he murdered another woman.
In Phoenix, Arizona, there is still a man at large who shoots people with a shotgun. He seems to predominantly target the Latina neighborhood.
Known as "Vampire of Dusseldorf” and the “Dusseldorf Monster", Peter Kurten murdered at least 9 people in 1929 in Germany. He was difficult to catch because he kept changing his weapon. He once released a woman named Maria, because she told him she couldn't remember his address.