On June 2, 1966, Betty Lou Zukowski of Chicopee, Massachusetts, was buried on what would have been her 11th birthday. Her body had been found, beaten and drowned, days earlier in the Westfield River. The killing would remain a mystery for 56 years—until Wednesday, when a grand jury indictment allowed officials to arrest Donald Mars, 73, for her murder. It’s unclear what evidence led the grand jury to indict Mars. He was first connected to the case in 1997, when police received information that resulted in a couple of witness interviews, but no arrest was ever made. Two years prior, Mars was convicted of raping a child, along with indecent assault and battery of a child under 14. “Sadly, Betty Lou’s parents are deceased and will not see Donald Mars answer for what we allege he did to their daughter,” Hampden District Attorney Anthony Gulluni said. “While this investigation will not bring Betty Lou back to her family, or grant her the opportunity to grow into a healthy adult that she and every child deserves, it is for them and for Betty Lou that we embark upon this journey of seeking justice.”