In Michigan, a naturalized citizen from Lebanon rammed his vehicle into a synagogue, where he was shot at by security before he shot himself to death.

In Virginia, a man previously imprisoned on a terrorism conviction was heard yelling “Allahu akbar” before opening fire in a university classroom in an attack that officials said ended when the shooter was killed by students.

The three acts of violence in the last week have laid bare a heightened terrorism threat unfolding against the backdrop of the U.S. war with Iran and as the country’s counterterrorism system is strained by the departures of experienced national security professionals at the FBI and Justice Department. The firings and resignations, along with the diversion of resources and personnel over the last year to meet other Trump administration priorities, have fueled concerns about the capability to head off a potential surge in threats.

“So much experience has been decimated from the ranks,” said Frank Montoya, a retired senior FBI official. “The folks that were best positioned to get to the bottom of it before something really bad happened” are in many cases no longer with the government, he said, meaning less experienced personnel assigned to the threat are “starting from way behind.”

The FBI said it would not comment on personnel numbers and decisions, but issued a statement saying “agents and staff are dedicated professionals working around the clock to defend the homeland and crush violent crime. The FBI continuously assesses and realigns our resources to ensure the safety of the American people.”

Iran has a history of plotting attacks, targeted killings inside the US

Iran has vowed revenge for the killing by the U.S. and Israel of Supreme Leader Ayatollah Ali Khamenei, and though the fighting has so far been confined to the Middle East, the Islamic Republic has long professed its determination to carry out violence on American soil.

Iranian operatives, for instance, responded to the 2020 assassination of Gen. Qassem Soleimani during the first Trump administration with a disrupted murder-for-hire plot targeting former national security adviser John Bolton.

A Pakistani business owner who says he was carrying out instructions from a contact in Iran’s paramilitary Revolutionary Guard was convicted in New York last week of trying to hire hit men in 2024 for assassination plots targeting public figures, including President Donald Trump, who was then running for president.

Though much attention has focused on Iran’s use of proxies or hired hands to carry out plots, the country’s capability to organize a large-scale assault on the U.S. remains unclear despite clear angst over the potential. The FBI warned in a recent bulletin to law enforcement about Iran’s aspiration to conduct a drone attack targeting California, but after the warning was publicized, officials emphasized the intelligence was unverified and that no specific plot was known to exist.

Lone actors have been a persistent concern for the FBI

The U.S. government after the Sept. 11, 2001, attacks overhauled its intelligence and national security apparatus to prevent similarly catastrophic events. But in the years since, lone actors radicalized online have nonetheless carried out shootings like the 2015 ambush attacks at a pair of military sites in Chattanooga, Tennessee and a rampage at an Orlando nightclub the following year by a gunman who killed 49 peopleand raged against the “filthy ways of the west.”

Those plots by self-directed individuals have proved notoriously difficult to prevent and have occurred even when the FBI has not been roiled by firings and internal upheaval like during the first year of the Trump administration.

“They’re self-directed,” said retired FBI official Edward Herbst. “That’s what makes them really lethal. You never know when they’re going to rise up. You never know when and where they’re going to attack.”

Terrorism concerns typically rise during times of international conflict when military action overseas is accompanied by increased vigilance, including outreach from agents to their sources, more active sharing of tips between federal and local law enforcement and closer coordination among FBI joint terrorism task forces, said Claire Moravec, a former FBI national security official who served as deputy homeland security adviser in Illinois.

Officials have said there is no indication that either the men arrested in connection with the explosives in New York, or the man responsible for Thursday’s Old Dominion University shooting, were motivated explicitly by the Iran war. The man who crashed into Temple Israel synagogue near Detroit on Thursday lost four family members in an Israeli airstrike in his native Lebanon last week, an official in Lebanon said.

Regardless, wars like the one in Iran can function as “accelerants,” raising the volume and intensity of grievances for the disaffected, Moravec said.

“Ultimately, the goal during these periods is not ‘surveillance’ but maintaining a broad awareness of how international events could translate into domestic security risks, so that threats can be identified and disrupted early,” she said in an email.

Resignations, firings at the FBI and Justice Department

The Justice Department’s National Security Division was established in 2006 to address threats of terrorism, espionage and other concerns. In the last year, lawyers in the division found themselves assigned to review the Jeffrey Epstein files to prepare them for release, and elite sections dedicated to prosecuting terrorists and catching spies have endured turnover.

About half of the division’s counterterrorism prosecutors have left since the beginning of the Trump administration, along with about a third of its senior leadership, according to estimates from Justice Connection, a network of department alumni.

A Justice Department spokesperson said the division’s singular focus remains “keeping the American people safe from threats foreign and domestic” and that there are no known or credible threats to the homeland.

FBI Director Kash Patel has fired dozens of agents, most recently about a dozen employees who worked on the counterintelligence investigation into Trump’s retention of classified documents at his Mar-a-Lago estate in Florida.

“This is not an exaggeration to say that they are not as capable as they were a year and a half ago,” Matthew Olsen, who led the National Security Division during the Biden administration, said this week on the Lawfare podcast, adding that “they’ve lost, forced out, fired, the most capable, the most experienced FBI agents, FBI officials and DOJ prosecutors, that were working on the Iran threat.”

In the national security realm, where experience and source development are vital, the loss of institutional knowledge and community relationships can be a crushing blow, said Montoya, the former FBI official.

“There was no transition,” Montoya said of the agents who have been abruptly fired. “These guys were just walked out of the building. The new guys can call them and say, ‘Hey, can you tell me what you were doing?’” but even so, “you’re still introducing a brand new face into the equation.”