Hoover also personally intervened to prevent federal prosecutions against the Ku Klux Klan members responsible for the terrorist bombing attack against the 16th Street Baptist Church. By May 1965, local investigators and the FBI had identified the perpetrators of the bombing, and this information was relayed to Hoover. No prosecutions of the four suspects ensued, however, even though the evidence was reportedly "so strong that even a white Alabama jury would convict". There had been a history of mistrust between local and federal investigators. Later the same year, J. Edgar Hoover formally blocked any impending federal prosecutions against the suspects and refused to share, with state or federal prosecutors, any of the evidence which his agents had obtained. In 1968, the FBI formally closed their investigation into the bombing without filing charges against any of their named suspects. The files were sealed by order of Hoover.