It was great to see how quickly law enforcement closed in on and arrested Ahmad Khan Rahami for the bombing in the Chelsea neighborhood of Manhattan that injured 29 people last Saturday night. It was more impressive in that it required the coordination of federal law enforcement authorities and those in two states.

Police have also connected Rahami, 28, to an explosion in Seaside Park, N.J., on Saturday morning and with bombs found in Elizabeth, N.J. He was taken into custody by police in Linden, N.J. after a shootout with authorities left him wounded.

Unfortunately, the bad news is that opportunities may have been missed that could have stopped Rahami before he planted the bombs at all. This and similar incidents raise the question whether federal authorities are being aggressive enough in assessing the dangers posed by those suspected of having terrorist sympathies.

The New York Times reports that when Rahami returned in March 2014 from a nearly year-long trip to Pakistan, customs officials flagged him and pulled him aside for additional screening. They notified the National Targeting Center, charged with assessing potential threats, the newspaper reported, citing law enforcement sources.

It appears that there were not enough red flags waving to pursue the investigation into Rahami further. That changed five months later when Rahami’s father told police, responding to a domestic dispute, that he was concerned about his son having terrorist sympathies.

According to the Times, this again led federal agents to examine Rahami's travel history, including a three-week trip he made to Afghanistan and another trip he may have made to Ankara, Turkey.

Apparently nothing came of it. Federal law enforcement authorities need to find out why and if there are lessons that can be learned to prevent future lone-wolf or small-cell attacks.

Rahami appears to fit a pattern of loner losers who are radicalized by the ranting of Islamic terrorist propagandists, heeding their calls to assist the Islamic State by committing violence in their home countries, be they in North America or Europe.

The FBI should be able to effectively profile personality traits that make certain individuals vulnerable to such messages. And when those traits match reports of someone having shown terrorist sympathies, the threat has to be taken seriously.

Unfortunately, an individual cannot be charged with having bad thoughts or even intentions, absent evidence of acting on those intentions. Federal agents will certainly re-examine any potential links between Rahami’s visits to Pakistan and Afghanistan and his subsequent actions.

What the United States should not do is the type of gult-by-association policy advocated by the Republican nominee for president, Donald Trump. The assumption that all Muslims are a threat until proven otherwise will only drive a wedge between law enforcement officials and the communities they need to provide vital information in identifying genuine threats by extremists.

In attacking Islam generally, rather than focusing on those segments within Islam that are using its religious cover for their evil intents and actions, Trump becomes a propaganda tool for the terrorists. There is nothing the Islamic State and like-minded groups want more than to turn this conflict into the West against Islam. They could ask for no better recruiting tool.

The Democratic nominee, Hillary Clinton, showed a measured response to the events in New York and New Jersey. She called for “smart enforcement, good intelligence” while keeping “in concert with our values.”

In the 15 years since the 9/11 attacks, U.S. intelligence and law enforcement officials have done a good job preventing another mass casualty attack. These lone attacks provide a new and more difficult challenge. The nation will not meet it by resorting to fear or by identifying the enemy in simplistic and broad strokes. It will meet it by remaining resolute in working to improve anti-terrorist capabilities, living fearlessly in refusing to alter our way of life, and rejecting the siren call of demagogues who claim any of this will be quick or easy.