WASHINGTON, D.C.: Vandals have broken and overturned more than 500 gravestones at a Jewish cemetery in Philadelphia, the latest in a spate of bomb threats and attacks against Jewish sites across the United States. Hundreds of headstones, some of them more than 100 years old, were cut in half, local media reported Sunday. A local rabbi, who was unnamed, told ABC television affiliate WPVI that the affected graves at the historic Mount Carmel Jewish cemetery in Philadelphia’s northeastern Wissinoming neighborhood also included those of one-time members of the Quaker and Muslim communities. New Jersey resident Aaron Mallin discovered the vandalism on Sunday when he came to visit his father’s grave at the cemetery. “It’s just very disheartening that such a thing would take place,” he told WPVI. Police say they are investigating the vandalism. The Anti-Defamation League has offered a $10,000 reward for information leading to the arrest and conviction of those responsible.