The Mystery of the Murder of a Family Member

There were some similar crimes that occurred between 1919 and 1922 close enough to the family's farm, but this information wasn't discovered by police. Internet sleuths later on, like in more recent years, have gone through German articles and linked the cases. The last attempt confirmed was by a group of new police who claim that they actually have evidence now of who the murder is. But they refuse to release the information because the suspect has since passed.