An explosion in New Jersey on Sept. 17 marked the start of a busy two days for grassroots jihadists in the United States — and for the law enforcement officers responding to the attacks. The 48 hours that ensued went as follows:
Saturday, Sept. 17
- 09:35 EST — Seaside, New Jersey: A bomb exploded in a plastic trashcan along the route of a planned 5K race for charity. Only one of the three pipe bombs bundled together detonated, and nobody was injured in the blast.
- 20:30 EST — New York: A pressure-cooker bomb exploded at a construction site in Manhattan's Chelsea neighborhood, injuring 29 people.
- 21:15 EST — St. Cloud, Minnesota: Dahir Adan stabbed 10 people at a mall before an off-duty police officer shot and killed him.
- 22:15 EST — New York: A concerned citizen reported a suspicious device on 27th St. in Manhattan, four blocks away from the site of the explosion earlier that evening. Police identified it as a second pressure-cooker bomb that did not detonate.
Sunday, Sept. 18
- The Islamic State-affiliated Amaq news agency claimed that the Minnesota attacker was a "soldier of the Islamic State." The media outlet, however, did not mention the New Jersey or New York attacks that occurred on the same day.
- 20:30 EST — Elizabeth, New Jersey: Two homeless men found a backpack containing five pipe bombs in a garbage can at a train station. Several hours later, one of the devices detonated while being handled by a bomb squad robot.
Monday, Sept. 19
- 08:00 EST — New York: Authorities publicly identified Ahmad Rahami as a suspect in the bombings and asked for the public's assistance in finding him.
- 11:00 EST — Linden, New Jersey: A police officer found Rahami sleeping in a doorway and captured him alive after a brief exchange of gunfire.
In the span of two days, both emergency situations were dealt with and the primary suspects were either taken into custody or killed. But the work is far from over for U.S. law enforcement. The old homicide unit motto goes, "Our day begins when your day ends," and the saying is no less true for the officials tasked with handling the long and difficult terrorism investigations ahead.
Cutting Through the Fog
Breaking events tend to be chaotic, and the reports that emerge from eyewitnesses and other sources often conflict with each other. One of the first things investigators have to do is cut through the fog and noise created by these accounts to figure out exactly what happened. Once they have constructed a coherent timeline, they can use it as a starting point to build on, turning to other questions such as who was responsible, what was the motive and how was the attack conducted.
At first glance, the case of the Minnesota knife attack may appear to be relatively straightforward. The perpetrator has been identified and killed, negating the need for a manhunt. The method of attack was simple and did not require much planning, preparation or weapons acquisition. Even so, investigators will need to dig deeper into Adan's motives as they search for signs of how he was radicalized and spurred to action.
Was he self-radicalized, or was he aided and encouraged by someone in his community who may be trying to incite others to launch similar attacks? Did he have contact with and receive direction from members of the Islamic State, or was he merely inspired by the group's rhetoric? Were there signs of his intention to conduct a terrorist attack that were either missed or disregarded?
The fact that the FBI has assumed control of this investigation shows that the agency is indeed working to answer these very questions.
Currently, no evidence exists that directly links Adan to the Islamic State. The group's propaganda outlet, however, has claimed that he was a "soldier of the caliphate" who carried out his attack "in response to calls to target the citizens of countries belonging to the crusader coalition." This is standard language used by the Islamic State to describe grassroots jihadists who have been inspired by the group rather than directed by it. Nevertheless, investigators will carefully review all of Adan's contacts, emails, social media posts, phone records and text messages for evidence of whether he was in contact with professional terrorists, recruiters or other like-minded individuals. Depending on his past activity, authorities may have to trace a slew of phone numbers, social media accounts and email addresses. They might also have to identify, locate and interview many different people, some of whom could live overseas. Even in the Information Age, investigating a relatively simple crime can become a laborious process, particularly when it is linked to terrorism.
Piecing Together the Evidence
Rahami's bombing spree will likely prove to be an even more complex case. In addition to the questions above regarding his radicalization and mobilization, a great deal of forensic work will need to be done on the devices he used. When bombs explode, their components do not vaporize; rather, they break apart and are scattered about the scene. Officials have already completed their search of the New Jersey and New York crime scenes and have recovered what pieces they could find, including explosive residue, explosive compound, container shards, added shrapnel, detonators, batteries, initiators, wire and tape. In fact, according to the criminal complaint filed in Rahami's case, officers found the cellphones from the two detonated devices and traced them to stores near Rahami's home. The complaint also said the cellphone used as an initiator for the unexploded pressure-cooker bomb in Manhattan was listed under an account belonging to one of Rahami's relatives (according to media reports, his father).
Detectives and lab technicians will now have to analyze the components they found. This can mean examining them for fingerprints, DNA, fibers and tool marks, as well as tracing items to the locations they were purchased or obtained from. In this particular case, the unexploded bombs will greatly aid investigators by providing important clues about the parts used in the devices that did detonate. The criminal complaint reports that authorities lifted 12 fingerprints from the unexploded pressure-cooker bomb, which enabled them to rapidly identify Rahami as the primary suspect. (The quick results are also a testament to the benefits of automated fingerprint databases.) That Rahami also bought many of the parts on eBay using an account in his name and had them shipped to his home address will speed along the investigation, too.
Though Rahami has been tapped as the main perpetrator in the bombing investigation, technicians will still have to sift carefully through the evidence to see if it indicates whether Rahami had help in constructing the bombs. Officials will likewise have to determine who purchased the bombs' components, as well as where and how they did it, to figure out whether Rahami had external support or financing. Meanwhile, authorities will look closely at Rahami's activities during his trips to Afghanistan and Pakistan. The latter will be of particular interest to law enforcement personnel, since the operatives who hatched the last two plots against New York — one by Faisal Shahzad that was botched and another involving Najibullah Zazi that was thwarted — received bombmaking training in Pakistan.
Because Rahami was captured alive, his interrogation will also be a crucial part of the investigation. Should he choose to cooperate, his interrogators may be able to help officials as they search for clues about Rahami's radicalization or any potential co-conspirators who may still be at large. But even if Rahami invokes his Miranda Rights, it appears from the facts laid out in the criminal complaint that authorities will be able to prove the allegations against him based solely on the evidence they already have.
With his fingerprints on at least one of the unexploded bombs, links between him and at least one of the cellphones, and closed-circuit video placing him at two of the crime scenes, it should not be difficult to build a prosecutable case — especially in the Southern District of New York, where the assistant U.S. attorneys and law enforcement agencies have decades of experience investigating and prosecuting terrorism cases.
In fact, it was this proficiency that helped authorities identify and track the suspect so quickly while liaising with the New Jersey officials who helped to locate and capture him.
Building a Solid Case
Officials will still be investigating the Rahami and Adan cases long after the media's attention has shifted to other stories. They will continue working methodically to piece together the events of Sept. 17-19, hunting down every possible lead well away from the glare of the international spotlight. That said, there are some things the investigators won't do. Acting under the supervision of the assistant U.S. attorneys, they will cautiously avoid any activity that could compromise the case against Rahami. After all, the rules of discovery mandate that everything the investigation team does must be turned over to the legal defense team.
With an eye toward successful prosecution, law enforcement personnel will likely also be reluctant to start the in-depth psychological and social evaluations that would help determine how and why Rahami was drawn to radical Islamist beliefs. Instead, these assessments — though useful for forming predictive analyses — probably will not begin until after Rahami is convicted and sentenced to what presumably will be a lengthy incarceration.