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

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.

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,