"At least 26 people were probably tortured, killed and then thrown into a pit," said head researcher Christian Meyer.
The 7,000-year-old remains from the Neolithic period were first dug up in 2006 in Schöneck-Kilianstädten, about 15 kilometres outside Frankfurt, but researchers later started to examine the bones more closely.
The assailants probably shot some of their victims with arrows made of animal bones and killed others with stone axes.
Of the 26 people, 12 to 13 were children, two were women and the rest were men. Both women were estimated to be over 40 years old.
"This could mean that the younger women were abducted during the attack," said Meyer, who began the research at the University of Mainz and presented the findings with colleagues in the US National Academy of Sciences journal "Proceedings".
"We found fractures in many skulls and especially in the calf- and shinbones," said Meyer, who specializes in analyzing bones. "These fractures must have been made with an enormous force", comparable to the power of a car.
A cranial fracture in the skull of a three to five year old child. Photo: DPA.
Even though after thousands of years the bones are not in very good condition, the researchers could still analyze what may have happened.
"We know that many people would have been killed by stone tools and probably died of skull injuries," Meyer explained.
The leg bones were also smashed in an almost systematic way.
Of course, Meyer and his colleagues cannot speculate about the motive of the assailants. They assume that an entire village was wiped out, which they said was not unique at that time.
"With the settled lifestyle, there were possibly conflicts over territories," Meyer said.
Schöneck-Kilianstädten is not the only site in central Europe of a Stone Age massacre.
Archaeologists have also found evidence of such violence in Talheim in Baden-Württemberg and in a village near Vienna.
"These three places prove that 7,000 years ago... there was already collective violence on a large scale," Meyer said. "This is probably connected to final disappearance of this culture."