A national security expert is urging the Department of Homeland Security (DHS) to raise the national terror threat level following a shooting that investigators say may be linked to terrorism, warning that sleeper cell activity within the United States poses an escalating danger.

“We are facing a wide variety of threats here, and the problem is, they’re all located within our own borders right now,” former DHS advisor Charles Marino said Monday.

Marino, a former Secret Service supervisory agent, joined “Fox & Friends First” following joint U.S.-Israeli strikes that killed several Iranian leaders, including Supreme Leader Ayatollah Ali Khamenei.

The unrest prompted retaliation threats along with warnings from security officials who say sleeper cells that have infiltrated the U.S. may be preparing to strike.

“There’s no doubt that law enforcement and intelligence agencies are operating at an elevated threat level here in the United States,” Marino said. 

“That’s based on the correct operating assumption that the United States has been allowed to be infiltrated with a myriad of threats from around the globe, thanks in large part to the policies of the Biden administration, which turned our borders into a sieve.”

Marino blamed several border policies for what he described as an increasingly vulnerable domestic threat environment, including “the undercutting and exploitation” of asylum and temporary protective status programs and weakness in the legal immigration process.

“What you have is you now have communities comprised of immigrants in the United States that have been allowed to segregate themselves based on culture and ideologies, and what this leads to is an ability to become radicalized,” he continued. 

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“And as reported, sometimes this radicalization is focused on those with mental health issues, those going through a tough time in their lives… this also impacts American citizens as well, who are open to becoming radicalized.”

Marino said he remains confident in federal law enforcement’s ability to respond but warned that potential adversaries could target critical infrastructure and cybersecurity systems.

He reiterated his call for DHS to formally elevate the National Terrorism Advisory System (NTAS) level and urged Americans to stay vigilant and cooperate with authorities.

Marino’s comments come as federal authorities investigate a deadly Texas bar shooting as a possible act of terrorism, while funding battles in Congress threaten DHS operations.

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Former ATF Special Agent in Charge Bernard Zapor warned Sunday that the U.S. faces growing vulnerabilities, particularly as DHS contends with funding uncertainty.

“It makes no practical sense whatsoever, and it puts our country and our communities down to something like a restaurant or a bar in Austin, Texas potentially at risk for a really unnecessary and ridiculous motive, I would say, political,” he said. 

“Our public safety has to be paramount above all. National security and public safety are the paramounts of our democracy, and it’s something we have to treat with ultimate care and that nothing like politics interferes with the ability to protect our citizens.”