The biggest America 250 Fourth of July security threat may be where protection is thinnest

Ahead of America's 250th birthday this weekend, agencies are prepared for the possibility of an attack on Fourth of July crowds and parade-goers.

That includes the Salute to America 250 Celebration and Fireworks in Washington, D.C., which the White House saids will be "one of the grandest displays of patriotism that the world has ever seen."

More than a million people are slated to gather on the National Mall to hear President Donald Trump speak and watch "the largest pyrotechnics display in the history of the world," the White House said.

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Jason Pack, a retired supervisory special agent with the FBI, told Fox News Digital agencies have likely been preparing and coordinating for the event for weeks, if not months.

"It's a whole of government approach, not just one agency," Pack said. "That's really important because that's how in the past [threats] were stovepiped and could have gotten missed."

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He said he has not heard of any specific threats, but anything is possible.

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"Given it's the Fourth of July, which is a holiday that's so special to the country, there's no doubt that someone would want to," Pack said.

While there will be heightened security in our nation's capital with millions of spectators expected to descend on D.C., experts say it's important to understand that smaller-scale events will also likely have amplified security.

Recall in 2022, a mass shooter opened fire on July Fourth parade-goers in Highland Park, Illinois.

Robert Crimo III was sentenced to life without the possibility of parole after court documents say he climbed on a roof above the parade and opened fire on spectators with a an assault rifle; seven people were killed and 48 others injured .

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Fox News Contributor and former NYPD Legal Bureau Commanding Officer Paul Mauro told Fox News Digital that it's imperative for local law enforcement to have safeguards in place to prevent tragedies.

Mauro urged small cities and governments to communicate with larger agencies.

He said, "Don't be afraid to ask the FBI office. Don't be afraid to talk to Homeland Security. They're there for that. Everybody is hyper aware of the fact that this is an iconic anniversary."

Mauro also said mass shootings are not the only risk to public safety.

In 2021, in Waukesha, Wisconsin, Darrell Edward Brooks Jr. drove an SUV into crowds of people at the Waukesha Christmas parade. Six people were killed and more than 60 others were injured.

Brooks Jr. is currently serving six consecutive life sentences. Mauro said that small towns, like Waukesha, and their police departments need to accept that terrorist attacks or similar incidents could happen in their communities.

He said the first step in preparing for such threats is acknowledging the possibility, rather than assuming "it could never happen here."

Once agencies recognize the risk, they can begin implementing appropriate security and preparedness measures.

Another example of attack by vehicle-ramming during a community celebration happened in 2017.

Sayfullo Saipov from Uzbekistan killed eight people and injured nearly 20 more when he rammed a truck into crowds of people at a Halloween parade in New York City. His devotion to ISIS was his alleged motive, the DOJ said; he's currently serving eight life sentences in federal prison.

While the truck ramming resulted in those eight lives lost, Mauro said the attack could have resulted in significantly more deaths.

He said that while serving in the NYPD Intelligence Bureau's counterterrorism unit, officials anticipated the possible vehicle-ramming attack. As a result, they hardened vulnerable parade routes by placing sanitation trucks and other heavy vehicles as barriers.

Saipov, who had rented a truck and planned to target a Manhattan parade, found the route blocked by these barriers and abandoned that plan. Instead, Mauro said, he drove along the West Side Highway in New York City, where he carried out a vehicle attack before being stopped after crashing into a school bus.

Mauro argued that because the attacker had no prior criminal or intelligence indicators, he was difficult to detect in advance.

He concluded that acknowledging the threat and implementing physical security measures prevented a much deadlier attack at the parade.

Looking ahead, one way that federal agencies and local police work together to thwart premeditated or organized attacks comes from the help of fusion centers, Pack said.

"Fusion centers" are located in various cities and larger urban areas "for the receipt, analysis, gathering and sharing of threat-related information between State, Local, Tribal and Territorial (SLTT), federal and private sector partners," according to Homeland Security.

If you see or hear about something suspicious ahead of the holiday, you can tip the FBI at tips.fbi.gov or by calling 1-800-CALL-FBI (1-800-225-5324)

For an immediate threat, call 911.