KENOSHA (NEW YORK TIMES) - Tapping on his cellphone with a sense of purpose, Mr Kevin Mathewson, a former wedding photographer and one-time city alderman in Kenosha, Wisconsin, did not slow down to fix his typos as he dashed off an online appeal to his neighbours.

It was time, he wrote on Facebook in late August, to "take up arms to defend out City tonight from the evil thugs".

One day earlier, hundreds of residents had poured onto the streets of Kenosha to protest against the police shooting of 29-year-old Jacob Blake.

Disturbed by the sight of buildings in flames when he drove downtown, Mr Mathewson decided it was time for people to arm themselves to protect their houses and businesses.

To his surprise, some 4,000 people responded on Facebook.

Within minutes, the Kenosha Guard had sprung to life.

His call to arms - along with similar calls from others inside and outside the state - propelled civilians bearing military-style rifles onto the streets, where late that night a gunman scuffling with protesters shot three of them, two fatally.

The Kenosha Guard then evaporated just as quickly as it arose.

Long a divisive figure in Kenosha, Mr Mathewson, 36, who sprinkles his sentences with "Jeez!" and describes himself as "chunky", does not fit the typical profile of a rifle-toting watchdog, although he said he supported President Donald Trump on Second Amendment grounds.

The rise and fall of his Kenosha Guard reflects the current spirit of vigilantism surfacing across the country.

Organisations that openly display weapons have existed for decades, with certain hot-button issues like immigration or Second Amendment rights inspiring people who think the Constitution is under threat.

Anti-immigrant and Islamophobic sentiments are rife, and some militant groups, like the Oath Keepers or the Three Percenters, train together under established hierarchies.

Ever since the 2017 white nationalist march in Charlottesville, Virginia, armed groups have become fixtures at demonstrations around the country, although membership numbers remain opaque.

Election tensions

With the approaching presidential election ratcheting up tensions in recent months, armed groups that assembled via a few clicks on the keyboard have become both more visible and more widespread.

Some especially violent groups were rooted in longstanding anti-government extremism, like the 14 men charged with various crimes in Michigan this month.

They included six accused by the FBI of plotting to kidnap Governor Gretchen Whitmer, whom the suspects had labelled a "tyrant" - framing their grievances in the vocabulary of the American Revolution.

Starting in April, demonstrations against coronavirus lockdowns prompted makeshift vigilante groups to move offline and into the real world.

That trickle become a torrent amid the nationwide protests after the police killing of Mr George Floyd in Minneapolis - with some armed groups claiming to protect the protesters while others sought to check them.

"They just spawn out of nowhere," said Mr J.J. MacNab, a fellow at George Washington University's Programme on Extremism.

When Mr Trump was asked at last month's presidential debate about activity by right-wing extremists, including the violence in Kenosha, he declined to outright condemn such groups.

His response - telling one far-right group to "stand back and stand by" - left experts who had already warned about the potential for greater violence before the Nov 3 election bracing for even more.

Experts who study violent groups say that many are technically not militias; they are too unstructured and do not undertake basic steps like training together.

They are usually just a fraternity with a shared goal, like the groups in Oregon that patrolled back roads amid wildfires, hunting mostly imagined looters or arsonists.

In Kenosha, police officers were caught on video expressing appreciation to the gunmen and handing them bottles of water, prompting criticism that law enforcement officers encouraged the armed groups.

But soon after, the sheriff tried to distance his department. "Part of the problem with this group is, they create confrontation," Mr David Beth, the Kenosha County sheriff, told reporters at a news conference.

Asked later about any investigation, the Sheriff's Department said it had not referred any cases linked to the Kenosha Guard for prosecution, and the Police Department did not respond.

Paramilitary groups

The Second Amendment may mention a "well-regulated militia," but all 50 states ban private paramilitary groups, said Mary McCord, a former senior Justice Department official now at Georgetown University Law Centre.

Some groups avoid calling themselves "militias" to circumvent the prohibition, experts said.

Mr Mathewson first tried to muster the Kenosha Guard in June after the city had small protests because of Mr Floyd's death in Minnesota. A little more than 60 people responded.

Then, on Aug 23, video emerged that showed a Kenosha police officer firing seven times toward Mr Blake's back.

When protests disintegrated into property destruction, Mr Mathewson said, he thought law enforcement was overwhelmed.

"Some people think that we should have left it up to the police, but I disagree. They were outnumbered. Our leaders failed us," he said.

After two nights of demonstrations, he posted an event on Facebook called "Armed Civilians to Protect our Lives and Property".

He named himself commander of the Kenosha Guard and added an open letter to police telling them not to interfere.

"That got a lot of traction," Mr Mathewson said. "Tons and tons of shares, likes, comments. I was receiving private messages to my Facebook page, my public figure page. They were just raining in."

Several hundred people volunteered to participate, and around 4,000 expressed approval.

His call to arms spread to other platforms, like Reddit.

Infowars, the website that traffics in conspiracy theories, amplified it, as did local right-wing radio stations.

Posts on Facebook amplified the sense of siege in Kenosha by spreading false rumours that murderous gangs from Milwaukee, Minneapolis and Chicago were coming to ransack the city of 100,000 people.

Ms Jennifer Rusch, 47, a hair stylist, clicked on Mr Mathewson's webpage to find armed men to protect her business. "Facebook had a lot to do with making everybody hysterical," she said. "Now we know 99 per cent of it was lies."

Flood of responses

People messaged Mr Mathewson from around Wisconsin and other states, asking where to deploy.

He could not handle the avalanche of responses flooding his cellphone, he said.

"People thought we had some kind of command staff or a structure, but it was really just a general call to arms" meant mostly for his neighbours, he said.

Mr Jerry Grimson, 56, a former campaign manager for Mr Mathewson during his run for alderman, responded by organising his own neighbours to come out.

"There was no way we were going to let people burn down our homes," he said. That night, Mr Mathewson stuck to the entrance of his subdivision, WhiteCaps, at least 11km from the city centre.

Witnesses blamed the violent disarray in Kenosha partly on the fact that many gunmen downtown were strangers to one another, with some on rooftops acting as spotters to call in reinforcements and no one in command.

To Mr Raymond K. Roberts, a real estate investor and six-year Army veteran who monitored the vigilantes, the parade of jacked-up pick-up trucks filled with armed men resembled Afghanistan.

"You have guys in the back of trucks, faces hidden, and you can tell that they are hunting," he said. Mr Roberts noticed that law enforcement officers largely ignored the men.

The gunmen never seemed to realise that all the combat weaponry made black residents like himself particularly uneasy, Mr Roberts said, and that the community would have preferred to protect itself.

"They just had this assumption that we don't exist," he said.

Homicide charges

As tensions surged, with protesters and armed enforcers tussling, the authorities say that Kyle Rittenhouse, a 17-year-old from nearby Illinois, opened fire with a military-style semi-automatic rifle, killing two protesters and seriously wounding a third.

He faces homicide charges and has become a poster boy for the far-right.

Mr Mathewson remains unsure which armed men downtown responded to his call, and he denied having any contact with Rittenhouse.

Mr Mathewson said what he did was covered by free speech. Despite rumours of widespread destruction, 95 per cent of the city remained untouched, noted the Rev.Lawrence L. Kirby II of the Acts Church.

"There was never a need in Kenosha for an armed militia to gather and to seek out any kind of vigilante justice," he said.

After the shootings, Facebook banned Mr Mathewson for life, removing his personal and professional pages.

He said he lost 13 years of photo archives, including videos of his daughter and son taking their first steps and a memorial page for his mother.

Mr Mathewson said that for now he had no plans to revive the Kenosha Guard.

His wife has had enough of the spotlight, he said, with his phone ringing constantly.

"I am getting love and hate from all over the country," he said.