The lake-studded commuter town of Mahopac, NY—once rated one of the best places to live in the country—seems an unlikely location for the outbreak of a second American civil war.

But for a few hours on Nov. 23, 2019, militia members and other far-right groups from across the country became convinced that Mahopac was going to be the 21st century’s Fort Sumter, set off by a seven-hour police standoff over a veteran’s Second Amendment rights.

Angered by a nationwide debate over “red flag” laws that allow law enforcement to confiscate firearms from people deemed to be a threat to themselves or others, far-right Instagram posters from the Three Percenter militia and other groups urged one another to drive to Mahopac from across the country and “shoot traitors.” By traitors, they meant police officers.

“Grab a gun and go to Mahopac,” wrote one Twitter user.

“Will Mahopac become the next Ruby Ridge?” asked another, referring to the fatal 1992 Idaho standoff between federal agents sent to enforce a gun charge and a far-right survivalist.

In reality, the Mahopac incident that thousands of right-wing internet users became enthralled by was actually a domestic violence investigation that had nothing to do with the Second Amendment. But the case became a viral flashpoint over gun laws anyway, thanks to far-right groups on social media and Instagram’s disappearing posts feature, Instagram Stories.

The standoff began around 2 p.m., when a police officer approached the home of 28-year-old Afghanistan veteran Alexander Booth to investigate a domestic violence claim against him. Booth refused to come out of his house, prompting police to set up a cordon around the home.

Booth broadcasted the beginnings of the standoff on his gun-themed Instagram account, “Whiskey Warrior 556.” Dressed in body armor and with what appeared to be a combat knife strapped to his chest, he claimed that the officers were citing a red flag law to take away a 30-round magazine that he owned.

In one post, Booth claimed that the incident could set off the “boogaloo”—a term widely used by far-right groups, including white supremacists, militia members, and extreme libertarians to refer to the kind of societal collapse or civil war that they’re anticipating. Other Instagram users quickly took up the charge, with one cheering that the still-ongoing standoff would be a “boogaloo catalyst.”

As police officers surrounded his home, Booth went viral in far-right social media communities. Before the standoff, he had only a few thousand followers on Instagram. But as the confrontation dragged on, he attracted national attention, crossing more than 130,000 Instagram followers.

“I’ve got the high ground, don’t underestimate my power,” Booth said in one post.

Booth published his address on Instagram, which was quickly circulated by his new social media allies. Instagram user @MrGunsnGear, who has more than 100,000 followers on the site, encouraged people to travel to Mahopac and “shoot traitors.”

The standoff also attracted attention from prominent right-wing figures. Gun Owners of America, a more extreme alternative to the National Rifle Association, tweeted that it was “monitoring the situation.” Enrique Tarrio, a Florida congressional candidate and the head of the far-right Proud Boys men’s groups, fumed over the standoff.

“This needs to F-ING stop NOW!” Tarrio wrote. “Red flag laws CANNOT be tolerated.”

As the standoff continued, Instagram users urged Booth not to surrender, warning him that police wanted to violate his Second Amendment rights. Booth posted pictures of the nearby police officers and called them “red coats”—a popular term on the right for law enforcement officials who enforce gun laws.

At the same time, Booth’s Instagram posts became more threatening. In one of his last posts, Booth warned that “there will be blood” unless he received a written notice from the police negotiator that he wouldn’t be charged. Booth’s supporters deluged the Putnam County Sheriff’s Office with phone calls and emails, overwhelming the department’s communications.

Booth eventually surrendered after seven hours. Putnam County Sheriff Robert Langley told The Daily Beast that Booth’s social media supporters made it harder for law enforcement officials to negotiate with him, and raised the possibility of violence around the scene.

“It compromised the ongoing negotiations with Alexander Booth,” Langley wrote in an email. “We strive for voluntary compliance exhausting all means necessary for a safe resolution and social media responses were only agitating Mr. Booth.”

The episode illustrates how social media—and its power to spread conspiracy theories and collective panic—can complicate both basic law enforcement functions and legislative efforts to deal with crises like gun violence. Red flag laws, which have been backed by congressional Republicans, have passed in 17 states and the District of Columbia. In almost every instance, their passage has been met with impassioned, sometimes violent, calls for defiance. Still, it’s unclear how much of that backlash exists only online.

Despite their online fervor, the vast majority of Booth’s supporters didn’t actually go to Mahopac. In a Facebook Live video posted the night of the standoff, a man claimed that he drove from another state to Mahopac to defend Booth. Once he arrived, though, he found that few, if any, Booth supporters had done the same.

In his video, the man fumed about the “fucking, no-show Patriot Three Percent militia,” a reference to a prominent militia group whose members had supported Booth online but apparently failed to materialize in large numbers in Mahopac. With no one else to rally with, the man settled for yelling “good job breaking your oath!” at nearby police officers before going home. A sheriff’s department in Putnam County, Florida, which had been besieged on Facebook by Booth supporters confused about which Putnam County they should be mad at, mocked the misguided critics as mere “keyboard warriors.”

The Putnam County, NY, sheriff’s office disputed Booth’s claim that his arrest had anything to do with the Second Amendment. No guns or magazines were found in his home, and Booth was eventually booked on charges in connection to the domestic violence case, including burglary, criminal trespass, and aggravated harassment.

After the standoff, many of Booth’s erstwhile supporters realized that he had duped them into turning his domestic violence case into a gun rights cause célèbre. Booth’s mentions on Instagram, which had initially called him a patriot willing to stand up to a totalitarian government committed to violating the Second Amendment, soon switched to comparing him to Jussie Smollett, the Empire star who allegedly faked a hate crime against himself.

Carmel Police Chief Michael Cazzari, whose jurisdiction includes Mahopac, agreed that social media users exacerbated the standoff.

“This is a person in crisis, having mental illness, having issues and he didn't need the people on social media telling him that his rights are being violated,” Cazzari said at a press conference. “He needed help. Medical help.”