New York City is one of many cities that have fallen victim to terrorist attacks in recent years. On a global scale, numerous attacks have been carried out using assault weapons, knives and even vehicles, which have been an increasingly common tool of terror. Perhaps more common than others over the years, the weapon of choice by lone wolfs and terrorist organizations has been the use of explosive devices. New York City alone has faced eleven mass attacks since the downing of the twin towers on September 11th, 2001 and seven of those have been carried out using explosive devices. Law enforcement officials are faced with immense challenges in defending and securing the streets of the world’s most densely populated areas, and the threat of attack with weapons of mass destruction (WMDs), bring added challenges to the everyday life of law enforcement officials. The question of how to prevent and respond to attacks with WMDs is one that does not have an easy answer. The cases of recent New York City bombings in 2016 and 2017 underscore the difficulties in finding the answer.

In 2016, Ahmad Khan Rahmi injured more than 30 people in the New York Metropolitan area by setting off three bombs in three different locations around the city. Rahmi’s bombs were made using common household goods and delivering methods/systems more suitable for traveling or cooking. Rahmi loaded the bombs into two suitcases and a backpack, items brought regularly along with passengers on their morning commutes to work or school and on their way back home at night – not items that are out of the ordinary. The bomb in the backpack was made with a pressure cooker.

One year later, in the fall of 2017, Akayed Ullah used Christmas lights and other common items to build a bomb that was meant to meant to cause an explosion that would kill many at New York’s Port Authority bus station. The Christmas decorations, pieced together with metal pipes, wire and metal screws luckily only injured three, and Ullah himself.

The materials used in both bombings were common household items, presenting one of the most difficult challenges facing those charged with the task of keeping our cities safe. Almost everyone has materials in the home or garage that can be weaponized with the right know-how. This know-how isn’t hard to obtain these days either, with YouTube videos and quick searches on the internet being all someone needs to turn holiday decorations and travel bags into weapons capable of causing mass casualties. In the case of Ullah, he had only been planning his attack for some months, a very small time frame to track down a perpetrator, especially if all they’ve done at the time is bought commonly sold goods at a local convenient store. The difficulty of stopping these bombs from being made is at best incredibly troublesome, especially in a city as populous as New York or London, where the number of individuals purchasing goods being capable of being turned into a bomb is immensely high and the ability of law enforcement to detect mal-intended purchases of these items being much lower.

Another difficulty adding to the trouble in securing city streets in large cities around the globe is that the individuals that carry out attacks may not even be on the radar of law enforcement, let alone a watch list or wanted poster. Both Rahmi and Ullah had no criminal records at the time of the bombings and therefore would have been out of the eye of law enforcement. This, in combination with the fact that the materials and time needed to carry out this type of attack are available to scores of people, makes the prevention of an attack a hard battle to win. Some individuals planning explosive devices are even in un-assuming positions within society.

Christian Toro and his twin brother Tyler were arrested by law enforcement for their part in attempting to construct a bomb made of explosive powder removed from fireworks. Christian, 27, was a high school teacher. The suspicion that those educating our youth are planning a mass attack on our cities is not one commonly held by the population and school teachers are not often placed on America’s most wanted. The discrete nature of Toro’s position almost allowed him to build a bomb; with the help of students he paid to remove the explosive material from the fireworks. To the credit of vigilant civilians and law enforcement however, the two individuals were not able to carry out yet another attack on New York City.

Easily available materials, under the radar individuals and how-to recruitment videos increasingly pushed by terrorist groups such as the Islamic State make the job of law enforcement ever more difficult. To defend against and respond to attacks with explosives andother WMDs, federal and local police, fire rescue and medical professionals need to be trained not only in the latest and most effective methods of response, but with the latest equipment. Common standards and effective trainings are just the first steps in defending our cities from attacks, but will go a long way in protecting the population.