His tenure as a top U.S. counterterrorism official coincided with the rise of the Islamic State, a wave of attacks in Europe, and a surge in terrorist recruiting through online propaganda.
But as Nicholas Rasmussen approached the end of his five-year run at the National Counterterrorism Center this month — including three years as director — he voiced concern that efforts to protect the United States from mass casualty attacks are being undermined by the nation's policies on guns.
"We find ourselves in a more dangerous situation because our population of violent extremists has no difficulty gaining access to weapons that are quite lethal," Rasmussen said this month. "I wish that weren't so."
His remarks represent a moment of rare candor by a senior U. S. intelligence official on an issue that is politically charged. Rasmussen, who has often tempered his public comments to avoid controversy, made the statement during a final briefing with reporters before his scheduled departure from NCTC on Friday.
Rasmussen, who is retiring, was among the few high-ranking holdovers from the Obama administration to remain in place for the first year under President Trump. He held senior positions at NCTC and the White House in both Republican and Democratic administrations during a 27-year career in government.
The Trump administration has not signaled who will replace Rasmussen at NCTC. The job will be held on an interim basis by the center's deputy director, Russell Travers, officials said.
The center was created after the Sept. 11, 2001, attacks amid sweeping reforms aimed at helping to improve coordination among spy agencies and the sharing of critical information about terror plots.
Those changes — combined with new laws, the war in Afghanistan, covert CIA operations overseas and massive investments in airport security in the United States — are widely credited with degrading al-Qaeda and reducing U.S. vulnerability to attacks of 9/11 magnitude.
The past decade, however, has brought new dangers driven by a surge in gun violence in the United States, including several high-profile attacks classified as acts of Islamist terror, without any comparable mobilization of resources or response. Counterterrorism officials have quietly voiced frustration about the matter for years.
"We definitely talked about it a lot," said Matt Olsen, who was Rasmussen's predecessor at the counterterrorism center. Rasmussen served as his deputy before stepping into the director position in December 2014. "For some it was a source of frustration that we couldn't do more."
Aspects of U.S. policy seem "irrational" when viewed from the counterterrorism perspective, Olsen said. Individuals who appear on the terrorism-related "no-fly" list are barred from boarding aircraft, Olsen said, but not purchasing a gun.
Agencies that scour databases for clues that radicalized individuals might be close to committing violence would probably be more effective if they could monitor weapons purchases, Olsen said. "But we really don't do that, because guns are just a third rail issue."
Gun rights proponents argue wider possession of firearms can help stop terrorist attacks. Some of the deadliest shootings in the United States in recent years, including the October attack in Las Vegas, were carried out by gunmen with no apparent tie to terrorist groups.
Rasmussen emphasized he could not offer any political solutions and law enforcement and national security agencies need to remain focused on preventing the spread of violent ideology — a mission he said has been complicated by anti-Muslim rhetoric.
Recent terrorist attacks in Europe and the United States have been built around crude plots using vehicles or other means to achieve mass casualties. Still, Rasmussen said, the connection between the abundant availability of weapons and the potential for violence is a simple calculation for counterterrorism analysts.
"More weapons, more readily available, increases the lethality of those that would pick them up and use them," he said. The United States' security measures and more integrated Muslim population are often credited with helping the country to avoid attacks like those in Paris and Brussels in recent years.
But Rasmussen said his overseas counterparts are sometimes astonished by the United States' approach on guns. He described a recent conversation with a security official in a country — presumably in Europe — with a significant radicalization problem.
"If we faced our terror threat with your level of access to firearms," the official said, according to Rasmussen, "We'd be in big trouble."