F.B.I. agents at the gay night club Pulse, in Orlando, Florida, where forty-nine people were killed in the deadliest mass shooting in American history. PHOTOGRAPH BY JOE RAEDLE / GETTY

On Sunday, around lunchtime, I took my two daughters and our puppy to a dog park in Brooklyn Heights, near the East River. It was a fine, breezy day, and throngs of people were strolling along the raised promenade, which provides a view of New York Harbor and downtown Manhattan. With Americans of all colors and creeds enjoying the sunshine, I felt like I was in an urban version of a Norman Rockwell painting.

Except, that is, for the iPhone in my pocket, which was providing updates from the attack at a gay night club in Orlando the night before: Twenty dead. Thirty dead. Fifty dead. Fifty-three wounded. Suspect named Omar Mateen, a twenty-nine-year-old American citizen of Afghan descent. The suspect’s former wife says that he beat her and wasn’t particularly religious. The suspect called 911 shortly before carrying out the massacre and pledged allegiance to ISIS. The suspect had been investigated by the F.B.I., twice. The suspect had legally purchased a pistol and an assault rifle a few days prior to the attack.

Looking at the stream of bulletins, it was hard to do anything but weep for the victims, their families, and the future of this country. But the fight soon began over who was to blame and what should be done.

The history isn’t really in dispute. It has been clear for years that the combination of America’s ludicrously lax gun laws and calls from Al Qaeda and ISIS for individuals, or groups, in Western countries to carry out terrorist attacks could produce horrific outcomes. For a time, the United States largely escaped such attacks, which have hit London, Paris, and many cities in the Middle East and Africa. But the country’s bizarre adherence to an expansive reading of the Second Amendment—a reading that the Supreme Court Justice Warren Burger described, in 1990, as a “fraud on the American public”—has left it acutely vulnerable to attacks by radicalized or disturbed individuals.

The shooting spree at Fort Hood, in 2009, which killed thirteen people, and the April, 2013, Boston Marathon bombings, which killed three people, hinted at what lay ahead. For whatever reason, the Tsarnaev brothers, at least one of whom appears to have advocated jihad, selected homemade explosives as their weapon of choice. But the seemingly endless series of mass shootings at schools, cinemas, churches, places of work, and other locations in the United States has shown us how deadly assault weapons can be. All that a U.S. citizen who wants to kill a lot of people has to do is drive to a local gun store, ask to purchase a couple of AR-15 rifles and some ammunition, pass a background check, get the weapons, and select a site. It is easier than hijacking a plane or assembling a truck bomb.

We have seen the pattern with guns play out repeatedly—three times in the past year with shooters who appear to have been influenced by ISIS or Al Qaeda, the casualty toll rising each time. Last July, Muhammad Youssef Abdulazeez, a Kuwaiti-born American citizen, opened fire on two military installations in Chattanooga, Tennessee, killing five people and wounding another two. A subsequent investigation found that he had a history of mental problems, and that he had legally purchased at least some of the guns he used, which included two assault rifles.

On December 2nd of last year, Syed Rizwan Farook and Tashfeen Malik, a married couple whom James Comey, the director of the F.B.I., subsequently described as “homegrown violent extremists,” opened fire at a government building in San Bernardino, California, killing fourteen people and seriously wounding twenty-two. It turned out that they had stockpiled a small armory, including two .223-calibre assault rifles, two semi-automatic handguns, and thousands of rounds of ammunition. They had purchased the handguns themselves, at a gun store called Annie’s Get Your Gun, while a neighbor had purchased the two rifles for them.

Four days after the San Bernardino shootings, President Obama delivered a prime-time address from the Oval Office, in which he said that Farook and Malik “had gone down the dark path of radicalization, embracing a perverted interpretation of Islam that calls for war against America and the West.” Obama called on Congress to “make sure no one on a no-fly list is able to buy a gun,” and added, “What could possibly be the argument for allowing a terrorist suspect to buy a semi-automatic weapon? This is a matter of national security.”

The Republican-controlled Congress ignored these words, just as it had frustrated the Obama Administration’s efforts to strengthen gun laws after the Sandy Hook massacre, which took place in December, 2012. “Sandy Hook marked the end of the US gun control debate,” Dan Hodges, a British journalist, tweeted in June of last year. “Once America decided killing children was bearable, it was over.”

If Hodges was right and the United States will never take action on gun control, then it is heading toward a future where much of the country is a fortified camp, with stricter rules governing who is allowed in, heavily armed police permanently patrolling urban hubs, more public buildings adopting airport-style security, and many more millions of guns sold, as alarmed citizens seek to protect themselves and their families against a perceived threat.

This is the low-trust equilibrium that Donald Trump and other supporters of “gun rights” appear to favor. Alternatively, the United States could respond to the deadliest mass shooting in its history by shaking off the straitjacket of the past, disproving the skeptics, and reforming laws that have proved to be a boon to those intent on doing harm. In this scenario, guns (particularly assault weapons) would be much harder to come by; borders would be secure, but not impermeable; heavy security would be focussed on vulnerable locations, rather than everywhere; and the burden of preventing terrorism and other violent attacks would fall on the police, the intelligence agencies, and a vigilant public.

In either of these versions of the United States, sadly, there would probably be more terrorist attacks, some of them carried out by U.S. citizens and inspired from abroad: nobody can disinvent ISIS, Al Qaeda, or the deadly sectarianism that these groups represent. Even if ISIS were to be soundly defeated in Iraq and Syria, diminishing its attractiveness to the young and impressionable, there would still be some people who sought to kill in its name. But the two versions of the United States would feel very different to live in: one would be more like other advanced countries; the other would be a nightmare.

Hopefully, the choice is still ours to make.