When Mrs Melania Trump released a rare statement on Monday deploring last week's storming of the Capitol and naming those who died, she started with Ms Ashli Babbitt, a 41-year-old woman who was shot and killed by a police officer as she tried to break open a door.

Ms Babbitt was reportedly not only a Donald Trump supporter, but also a QAnon adherent.

Separately, a 41-year-old man, one of the first to break into the building and who two days later surrendered to the police in his home town of Des Moines, Iowa, wore a QAnon T-shirt at the invasion of the Capitol.

Investigators said he told them he "wanted to have his T-shirt seen on video so that 'Q' could 'get the credit' ", Federal Bureau of Investigation (FBI) special agent Julie Williams wrote in a statement.

QAnon is a loosely connected, cult-like, rambling network of conspiracy theories. Once delegated to the fringe, it has been veering into the mainstream.

At least two QAnon supporters are in Congress: Ms Marjorie Taylor Greene of Georgia and Ms Lauren Boebert of Colorado, who last week threatened to bring her Glock pistol to Congress in violation of District of Columbia laws.

The "Q" identity belongs to an anonymous online presence that is active on fringe forums, posing as someone with high-end military clearance in the Trump administration.

Among other things, QAnon adherents believe in the existence of a deep-state cabal of paedophiles and child traffickers, led by prominent liberals. And many believe Mr Trump has been divinely sent to save the children.

"QAnon isn't just a right-wing phenomenon, although it's disproportionately right wing because they think that Trump is the saviour, plus he is here to save the children," says Dr Mia Bloom, terrorism expert and professor of communications and Middle East studies at Georgia State University.

"Donald Trump has been very effective at bringing together a diverse coalition of people, whether they're anti-government militia… (or groups like) Boogaloo, Three Percenters, Oath Keepers, neo-Nazis. The something-in-common that they found was a second term for Donald Trump."

In December 2016, soon after Mr Trump won the election, a 29-year-old North Carolina man drove for several hours all the way to Washington DC and fired a military-style assault rifle inside a pizzeria, wrongly believing he was saving children trapped in a sex-slave ring.

The incident was dubbed "pizzagate". The man was sentenced to four years in jail.

In July last year, a man rammed a pickup filled with guns through the gates of Canadian Prime Minister Justin Trudeau's home, then fled on foot with a rifle. The police managed to arrest him.

Just 35 minutes before the incident, he had posted on Instagram a conspiracy theory about global elites creating Covid-19 - crediting the unknown "Q".

The FBI considers QAnon a domestic terrorism threat. At a congressional hearing in September on threats to the homeland, FBI director Christopher Wray said the bureau views it as "less of an organisation and more of a complex set of conspiracy theories".

Many of the acts of violence QAnon has inspired have been perpetrated by women, warned an article last month for NBC News, co-authored by Council on Foreign Relations (CFR) adjunct senior fellow Farah Pandith, CFR research associate for counter-terrorism Jacob Ware and Dr Bloom.

A female QAnon supporter carrying a dozen knives was arrested in May last year when she live-streamed a trip to New York City to "take out" then candidate, now President-elect, Joe Biden.

In August, another QAnon adherent was charged with aggravated assault in Texas after allegedly ramming her car into people she believed were involved in the kidnapping of children.

Ominously, QAnon theories have been flooding right-wing circles on the Internet with increasing intensity since the storming of the Capitol.

"The First Lady sort of made an equivalence between the people who were storming the building that got killed and the police officers in the Capitol that were killed," noted Dr Bloom.

"That creates perverse incentives, because like with any other group, you have people that are kind of delusional, who will convince themselves that it is personally up to them to affect change, which is the explanation for 'pizzagate'," she told The Straits Times.

When Mr Trump was asked about QAnon in August last year, he said: "I don't know much about the movement, other than I understand they like me very much. Which I appreciate."

"He's incited them," contends Dr Colin P. Clarke, director of policy and research at The Soufan Centre, a global security consultancy. "It's not a dog whistle; it's a bullhorn."

The movement has been underestimated because it is easy to be dismissive of the conspiracies it peddles, Dr Clarke told ST.

"But that does not make the threat any less potent. Just because the beliefs are far beyond the pale doesn't mean they are not capable of violence; they've proven it again and again.

"As dangerous as they are, at least you know what anti-government militias stand for and want. With QAnon, what policies can you possibly implement to assuage their grievances, since what they believe in doesn't exist?"