There are two questions: Did terrorism suspect Ahmad Khan Rahami plant bombs in New Jersey and New York—one of which exploded in Manhattan's Chelsea neighborhood, injuring 29 people? And if he did, will authorities be able to discern why he did it?

The FBI's Boston office is assisting with the investigation. And, as seems intuitive, the New York incident is being compared to Boston’s own encounter with terrorism on Marathon Day four years ago. Rahami and Tamerlan and Dzhokhar Tsarnaev used pressure cooker bombs, were naturalized American citizens turned jihadists, engaged in shootouts with police, and were apprehended with the help of surveillance cameras.   

Standing at the Boston Marathon finish line, local resident Tamario Merrit said the improvised bombs left in New York and New Jersey last week triggered emotions similar to those he felt on April 15, 2013.

“It resonates deeply because of the fact that it’s very alarming for someone to set off an entire dumpster as an explosion," Merrit said. "That’s just a small example of what could happen in a major city. So yes, I have concern here in Boston as well.”

But another resident, named Bruce, also standing at the finish line—in the sight of new surveillance cameras focused on that spot—found little resonance with New York.

“Well, I believe that with so little information reached so far in those incidents that it’s difficult to make the connection to the Boston Marathon Bombing," he said. "You know, there are incidents that happen throughout the world and it’s hard to make a specific connection of each incident to the Boston Marathon bombing.”

Paul Cathcart of Cambridge concurred.

“It didn’t make me think of the bombings here, though I’m obviously in solidarity with the city," he said. "The same busy part of town, the same sad thing, but fortunately no one was killed.”

Many, however, have been less thoughtful about the implications of this latest act of terrorism.

Islamic organizations in the U.S. are concerned about what they view as simplistic scapegoating—on social media and elsewhere—surrounding the bombing, as well as the ISIS-inspired stabbings in St. Cloud, Minn. These incidents come amidst a spate of anti-Muslim hate crimes around the nation, according to the FBI and the Council on American Islamic Relations.  

Before Rahami’s arrest, Juliette Kayyem, a former Homeland Security official and a WGBH News contributor, cautioned the public, the media, and politicians against jumping to conclusions about the motivations behind the terrorist assaults on New York and New Jersey.

“The only explanation we should care about as a nation is the accurate one," Kayyem said.

Arie Perliger, a terrorism expert from Israel and a professor at the University of Massachusetts Lowell’s Center for Terrorism and Security Studies (CTSS), told WGBH News just before Rahami’s arrest that like the bombs left by the Tsarnaevs near the Marathon finish line, those planted in New York and found in New Jersey were crude.

“It seems like this was perpetrated by someone who had limited training or limited experience," Perliger said. "Both attacks seemed somewhat sloppy."

What the New York explosion has revealed is just how easy it is to the build a bomb. The improvised pressure cooker bombs left in Chelsea, like those constructed by the Tsarnaev Brothers, were filled with shrapnel. We learned at the trial of Dzhokhar Tsarnaev that the brothers obtained knowledge of explosives through an al-Qaida published pamphlet authored by an American radical cleric, Anwar al-Awlaki, “How to Build a Bomb in the Kitchen of Your Mom.” Rahami, we have learned, also read the works of al-Awlaki.

“Unfortunately, there is information out there through the internet and other sources that provide some information and guidance on the construction of devices”, said former Massachusetts State Police chemist Adam Hall. Hall runs the forensics lab at Northeastern University, and has provided expertise on how the bombs set off in Boston were made.

At the Boston Marathon finish line, Petra, a tourist from the Czech Republic, said prior to coming here she read all about the Tsarnaevs and their bombs. But her mind was on the city south of here. She said after this weekend's explosion in Manhattan she’s fearful of traveling to New York.

“I mean it’s a dangerous city or worse, so anything can happen there," she said. "It feels much safer here, definitely.”

Fear is exactly what terrorists hope to achieve, say experts. And regardless of who sets off bombs, the question is whether they will have succeeded.