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.

"We are enhancing security measures and coordinating intelligence-sharing to proactively address potential risks," a DHS spokesperson told Newsweek.

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.