Attacks perpetrated by lone actors are the biggest terrorism threat to July 4th festivities in New York City and elsewhere, federal authorities said in a threat assessment obtained by CNN.

In a joint bulletin, the FBI, Department of Homeland Security and other law enforcement agencies said individuals or small groups motivated by political, racial or personal grievances are most likely to target large gatherings like the Macy’s fireworks show in New York City, or other celebrations across the country.

A lone wolf actor poses the biggest threat to Fourth of July celebrations in New York and San Francisco, according to multiple intelligence bulletins obtained by ABC News. The Department of Homeland Security and the FBI are concerned about the potential for copycat attacks from the New Orleans terror attack on New Year's Day,