The Jane Jacobs School of Counterterrorism

People stand behind police lines as firefighters, emergency workers, and police gather at the scene of an explosion in Manhattan on Sunday.

Spencer Platt/Getty Images

Ahmad Khan Rahami, who was arrested Monday morning in Linden, New Jersey, is suspected of leaving bombs in four separate locations in New York and New Jersey on Saturday.

Two bombs exploded, the first in a garbage can in Seaside, New Jersey, on Saturday morning, causing no injuries, and the second in a dumpster in Manhattan on Saturday night, causing 29 injuries. No one was killed.

The other two bombs were discovered before they could go off—not by the America’s largest police force, or by our billion-dollar surveillance state, but by curious bystanders. They weren’t thieves, as news outlets reported initially, but scavengers. Call it the Jane Jacobs School of Counterterrorism, after her recognition that civilians, not police, operate the most effective surveillance.

Shortly after the explosion on 23rd Street, police canvassing the neighborhood discovered a second bomb four blocks away. According to the New York Post, surveillance footage from that evening shows that two men had removed the bomb from a suitcase earlier in the evening, possibly disabling it in the process, and leaving with the bag.

The bombs at the Elizabeth, New Jersey, train station were discovered later that night under similar circumstances when two men pulled a backpack from a garbage can, thinking it might contain something of value. They walked a short distance with the bag before opening it, seeing wires and pipes, and calling the police. The bag, the FBI later determined, contained five bombs.

Sure, these weren’t exactly Jacobs’ benevolent neighborhood stevedores, or the citizen watchmen summoned by the Metropolitan Transportation Authority’s “If You See Something, Say Something” campaign (which has since been taken up by the Department of Homeland Security). More likely, they were the kind of canny, observant loiterers, looking for a hustle, that police tend to chase from public places.

Jacobs’ “eyes on the street” theory is often associated with a modest public code of deterrence—a silent enforcement of neighborhood values. The MTA’s “See Something” catchphrase has been called Orwellian, encouraging New Yorkers to harbor suspicions bordering on paranoia.

Real public safety functions somewhere in between, as Jacobs observed in her 1961 urbanism opus The Death and Life of Great American Cities. “Safety on the streets by surveillance and mutual policing of one another sounds grim, but in real life it is not grim,” she wrote. “The safety of the street works best, most casually, and with least frequent taint of hostility or suspicion precisely where people … are least conscious … that they are policing.” (Australia’s “Eyes on the Street” campaigns, in their formalization of the police-community relationship, are in some ways a perversion of her theory.) In Jacobs’ view, lively streets deter, without any kind of official protocol, not only broken-windows offenses like public urination but also more serious crimes like child abduction.

It was one such instance of accidental policing that led the NYPD to a Times Square car bomb in 2010, when a pair of nearby street vendors noticed a smoking Nissan Pathfinder on Broadway. There was a bomb inside.

Vendors, trash rummagers: These are the people most often subject to police scrutiny and harassment, chased from hypersecure places where emptiness is considered a mark of safety. Their vigilance would be an awfully cynical reason to be more supportive of their right to public space. Let it simply function as a reminder of what we have in common with the eyes on the street, whomever they may belong to. In this case, we should thank them.

Read more from Slate on the bombings in Manhattan and New Jersey.