The initial reaction to news that reputed Gambino family crime boss Frank Cali had been fatally shot outside his home on Staten Island was to wonder whether New York City might be back on the brink of a mob turf war. There is a pattern to these things that, while dormant, is familiar: A crew whacks a gangster, and his crew retaliates. They go to the mattresses. They hunker down at the Bada Bing.

It soon became clear that this incident was not like the ones we see in movies. Shortly after Cali's death, a 24-year-old named Anthony Comello was arrested in connection with the crime. Mr Comello did not have the résumé of a Mafia button man. In fact, it was reported that police believe he killed Cali because the crime boss would not let Mr Comello date his niece.

When Mr Comello appeared in court in New Jersey for an extradition hearing that would send him back to New York, he suddenly displayed a hand covered in scribbled text.

"United we stand," he had written, along with "MAGA forever" - a reference to President Trump's campaign slogan, "Make America great again."

Drawn with thick lines at the centre of his hand was a large "Q."

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Last summer, there was a flurry of reporting on "QAnon," when adherents began popping up at Trump rallies. It is a sweeping, bizarre theory that Mr Trump's presidency was secretly predicated on uprooting child molestation rings and in which an anonymous figure named Q revealed secret messages from within the White House about Mr Trump's hidden agenda. A president who had based his election on the idea that he was battling a nefarious establishment cabal had transformed, in the eyes of thousands of supporters, into a president battling an even more dangerous and toxic group, leaking The Truth out to a select few through this anonymous account.

That Mr Comello was sporting a "Q" on his hand in court, though, was not an ironic statement or a wink at the broader conspiracy theory. In a phone call with The Post on Thursday, his attorney, Robert Gottlieb, argued that the QAnon theory was central to the incident on Staten Island.

"The evidence that I refer to, the QAnon, the other hate words and messages emanating from other extreme right-wing conspiracy websites, as well as statements made by the president, without any question will be critical and central to explaining what happened in this case," Mr Gottlieb said.

The lawyer did not explicitly state that Mr Comello had committed the crime, but he added, "What I can say unequivocally is: Whatever happened here is connected to those hate messages and websites."

After Mr Comello was arrested, the government seized his computer, and Mr Gottlieb indicated that he had not seen the specific online material Mr Comello had reviewed. But he did indicate that Mr Comello participated in the QAnon world, either passively or actively, a fact he learned from speaking to Mr Comello's family and friends. They apparently indicated to Mr Gottlieb that, in recent months, they had noticed a change in Mr Comello's behaviour that they attributed to his online activity and involvement with the unnamed sites.

Obviously, there is a potential benefit to Mr Gottlieb's client in presenting him as having psychiatric problems. Mr Gottlieb did not shy away from that suggestion.

"This is a very complicated psychological and psychiatric issue," he said. "The hate messages, the venom that is spewed on the Internet doesn't necessarily affect everybody. It certainly has a greater chance of having a devastating impact on someone who may be suffering from psychiatric problems."

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"It has a real impact on the most vulnerable people, who, if touched and affected by the hate, can do things which if they were not suffering from the mental illness they would have never done," Mr Gottlieb added.

This would not be the first time that someone appears to have been inspired by right-wing online conspiracy theories and Mr Trump's rhetoric to take violent action.

One week ago, Cesar Sayoc pleaded guilty to charges that he had sent explosive devices to newsrooms and Democratic politicians across the country last fall. An armed man who blocked traffic near the Hoover Dam last year cited QAnon slogans in letters he later wrote. After several violent threats in September, Reddit banned some QAnon discussion groups.

Mr Gottlieb was careful in how he described what happened on Staten Island and its relationship to his client. He was much less worried about linking what his client read online to the possibility that it affected how Mr Comello behaved.

"Over the past few years, people have been talking about the danger of this garbage that's on the Internet," Mr Gottlieb said. "This could very well be the case that reflects that words really do matter."