Federal authorities are seeking two unidentified men in connection with the Boston Marathon bombing, their faces recorded with striking clarity by street video surveillance cameras and their images dramatically revealed early Thursday evening at a press conference in Boston.
Both suspects, who were observed walking through the crowd of spectators at the marathon, wore dark jackets and carried backpacks. The first man, dubbed Suspect One by the FBI, had a dark cap and khaki pants. The other, called Suspect Two, wore a backward white cap and was seen leaving a backpack near the site of the second of the two explosions.
At the press conference, Boston FBI chief Richard DesLauriers presented still images and video – both posted to the FBI website – that show the two men walking together, one following the other. Investigators earlier had displayed pictures of charred and blasted parts of a black nylon backpack retrieved after the explosions, which killed three people and wounded 176 others Monday afternoon.
Mr. DesLauriers said both men are considered armed and extremely dangerous and warned the public against approaching either man. He requested that anyone with information about the men should just contact the FBI.
Although not depicted in the pictures or video released Thursday, one suspect is seen in a video still held by the FBI setting down a backpack at the site of the second explosion in front of the Forum Restaurant, DesLauriers said. Both suspects appear to be walking together through the marathon crowd on Boylston Street in the direction of the finish line, he said.
Picking out two suspects from thousands of people in the crowd required painstaking analysis and the sifting of thousands of videos and pictures submitted to authorities by the public and taken from surveillance video cameras.
“Within the last day or so, through that careful process, we initially developed a single person of interest, not knowing if the individual was acting alone or in concert with others,” DesLauriers said. “We obviously worked with extreme purpose to make that determination ... and through that process the FBI developed a second suspect.”
As the official investigation moved forward, a parallel probe was being carried out by amateur sleuths online. The armchair detectives are busy analyzing the many photos available online, showing the Marathon Day finish line both before and after the blasts.
In effect, the investigation has become partly “crowd-sourced” – farmed out (intentionally or not) to public forums where people are sifting photos for clues. Many images are now annotated with colored circles around potential clues, such as an individual labeled with “bag” in one photo and “no bag” in another.
In the parallel probe by the online community, various white-hatted individuals have been identified in photos of the scene. DesLauriers warned the media and the public that only the video images on the FBI website were reliable for purposes of identification.
“The photos and videos are posted for the public and media to use, review and publicize,” he said. “For clarity these images should be the only ones – I emphasize the only ones – the public should use to assist us. Other photos should not be deemed credible, and necessarily divert the public’s attention in the wrong direction and create undue work for vital law enforcement resources.”
What’s become crystal clear in this case is the critical role of surveillance footage recorded by closed-circuit television (CCTV) security cameras along the street.
Deciding to release such photos would be a tough call for investigators worried that doing so might prompt suspects to run, security experts said. But that concern seems to have been outweighed by the advantage of having millions on the alert and watching out for them.
Propelling the high-speed hunt has been a digital revolution in video forensics software analysis tools. To find these strikingly clear images, investigators pored over mountains of video and still-picture images submitted by the public and television crews at the urging of the FBI. But with thousands of hours and images reportedly being analyzed, sifting that mountain of images for tiny details that might be meaningful has undoubtedly required computers loaded with powerful video forensics software, those who use that software say.
“Investigators have so many videos to look into, so many hours. Our software will basically digest all the objects in the original videos so that in the end you’re left with a minute of video instead of hours. When you find a person of interest, you can watch their actions that may have occurred over several days across multiple cameras in just a few minutes.”
Automated forensics tools have undoubtedly been a key aid to investigators in identifying suspect footage provided by CCTV surveillance cameras deployed by store operators near the finish line, Mr. Gavish and others who use such systems say.
High-resolution CCTV video, deployed in public spaces to help deter crime and terrorism, has in a number of cases internationally helped sort out chaotic events and help identify terrorism suspects – and has become part of a vigorous debate over terrorism policy.
On July 7, 2005, in London, three bombs exploded on three underground trains, and one bomb exploded on a bus, killing 52 commuters. Identification of the four suicide bombers in that attack relied heavily on CCTV footage.
But the real test came two weeks later on July 21, with four more attempted bomb attacks on the London transportation network. In the wake of that attack, CCTV images of four suspects were released. All four eventually were arrested.
Such successes have led to a vigorous policy debate over whether to more widely deploy CCTV cameras to monitor public spaces to deter crime and identify perpetrators, including terrorists. But while widely deployed in European cities, such CCTV systems have not been deployed en masse in the US, in part over concerns about infringing civil liberties.
As a result Boston, like most US cities, is peppered with private CCTV systems deployed mostly by shops and retailers, but has relatively few deployed by government authorities. Critically, the cameras are not networked into a cohesive system that integrates image collection and analysis. Exceptions include Baltimore, Washington, Chicago and a few others with extensive CCTV systems.
“Chicago has really done this, and so have a few other cities with some success,” says Adam Thermos, founder of Strategic Technology Group, an international security firm that specializes in large-scale, citywide CCTV deployment.
“I did an assessment for Boston a few years ago,” he says. “Really, it’s below par in terms of integration of systems that are available – and the overall number of cameras. This is why the FBI is asking citizens to give them homemade videos and from stores. They shouldn’t have to do that.”
Others are less sure about that. European researchers who have studied the effectiveness of CCTV systems on deterring terrorism have obtained mixed results and concluded that such cameras might even attract terrorists.
“We expect CCTV to have less of a deterrence effect in the case of terrorism than in the case of street crime,” researchers at the University of Basel wrote in the findings of a 2011 study.
While CCTV “might facilitate the attribution of attacks to specific terrorist networks,” the researchers also noted that “terrorists paradoxically often actively exploit both of these aspects: They choose locations and targets as well as the timing of attacks in order to generate as much media attention as possible.”
Whether surveillance video proves to be the critical break in the marathon bombing case is not yet known. But it will certainly pique interest in CCTV systems and accelerate US debate over their merits.
A 2011 Urban Institute report on CCTV effectiveness in several US cities did find that crime declined in some areas with CCTV deployment. “Surveillance cameras alone are a not a silver bullet,” the report said, “but simply another crime control and investigative tool.”
Maybe not, but the FBI’s DesLauriers says it’s vital.
“For more than 100 years, the FBI has relied on the public to be its eyes and ears,” he said. “With the media’s help in an instant these images will be delivered directly into the hands of millions around the world.... Though it may be difficult, the nation is counting on those with information to come forward and provide it to us.”