The famous case of three civil-rights activists murdered during Freedom Summer is officially concluded, Attorney General Jim Hood announced Monday.

No living suspects remain to bring charges against for the lynchings of James Chaney, Andrew Goodman and Michael Schwerner, who disappeared on June 21, 1964, Hood said. Their bodies were found a month and a half later beneath an earthen dam.

“The FBI, my office and other law enforcement agencies have spent decades chasing leads, searching for evidence and fighting for justice,” Hood said in a news release. “It has been a thorough and complete investigation. I am convinced that during the last 52 years, investigators have done everything possible under the law to find those responsible and hold them accountable; however, we have determined that there is no likelihood of any additional convictions. Absent any new information presented to the FBI or my office, this case will be closed.”

Hood said investigators were interviewing witnesses in the case as recently as 18 months ago. In 2005, state and Neshoba County prosecutors tried Edgar Ray Killen, who orchestrated the murders. Killen was convicted of manslaughter and sentenced to 60 years in prison; he is 91 years old and eligible for release in 2027.

Two other men, Jimmy Lee Townsend and Pete Harris, are suspected to have direct knowledge of the murders, but there isn’t enough evidence to bring charges against either, Hood said.

The federal Emmett Till Unsolved Civil Rights Crime Act of 2007 allowed investigators to continue working on the case, Hood said. Bills to reauthorize the act have been introduced in the U.S. House of Representatives and Senate, where both Mississippi senators have endorsed its passage.

Hood said closing the case involves filing a final report with the U.S. Department of Justice as a historical record.

“Kids will know the federal government did everything possible to prosecute this case,” Hood said.

He added that while the case is being closed, it could be reopened if prosecutors uncover new evidence or witnesses come forward.