Anthony Comello went to Francesco Cali’s house on Staten Island to arrest him. Cali was understood by law enforcement to be a boss in the Gambino crime family in New York, linked to the Sicilian Mafia directly. He had done time for extortion in the past, so the NYPD effecting a new arrest probably wouldn’t have surprised many people.

Except that Comello isn’t a police officer. When he went to Cali’s house in March, he was just a guy who spent a lot of time tracking national politics and reading conspiracy theories online. According to a filing submitted by his attorneys, Comello believed that Cali was part of the “deep state” and an integral part of the “QAnon” conspiracy, a sprawling theory centered on child sex abuse that has been propagated by an anonymous Internet poster called “Q.” An Instagram account belonging to Comello includes a number of images of Q posts alongside video snippets of President Trump speaking and images of Fox News broadcasts and personalities.

The Cali encounter was not Comello’s first attempt at taking the law into his own hands, the filing says. In February, he showed up at Gracie Mansion, the home of New York Mayor Bill de Blasio, in an effort to take de Blasio into custody for alleged election fraud. A bit later, Comello believed that Reps. Maxine Waters (D-Calif.) and Adam B. Schiff (D-Calif.) were in Lower Manhattan, so he went to a nearby U.S. Marshal’s office to ask their help in arresting the lawmakers.

Comello believed that all of them “were actively trying to bring about the destruction of America,” according to his attorney. Comello’s family had noticed “changes to his personality” after Trump’s election, the filing states, and that Comello “began to take an interest in politics, something he had not previously been involved in.”

A few months before Comello’s attempted citizen’s arrests, Waters was the target of pipe bombs sent to her congressional offices in California and Washington. Those devices were constructed by Cesar Sayoc, as Sayoc has admitted. They were among several devices made by Sayoc as part of a campaign of fear that played out shortly before the midterm elections.

A court filing from Sayoc’s attorneys submitted Monday offers a somewhat similar pattern to that which preceded Comello’s attempt to arrest Cali. Sayoc was a Trump fan before the president’s entry into politics and supported Trump’s campaign once it began. Sayoc “began watching Fox News religiously at the gym, planning his morning workout to coincide with Fox and Friends and his evenings to dovetail with Hannity,” according to his attorneys. Because of “his cognitive limitations and mental illness,” Sayoc believed fake news reports that he read online, “which increasingly made him unhinged.”

"His paranoia bled into delusion and Mr. Sayoc came to believe that prominent Democrats were actively working to hurt him, other Trump supporters, and the country as a whole,” the filing reads. “Mr. Sayoc became obsessed with this idea and found himself unable to think of anything else.” He built pipe bombs, none of which detonated.

Francesco Cali, though, is dead, shot by Comello outside his house. When Comello tried to arrest Cali, Cali understandably resisted. Comello thought the alleged mobster was reaching for a weapon, his attorneys claim, prompting him to retrieve a gun from his truck and fire. Comello is facing murder and gun charges.

It’s not clear the extent to which either Comello or Sayoc suffers from diagnosed or diagnosable mental illness. There is obvious motivation for their attorneys to present them as not being responsible for their actions. But it raises a question that has been a subtext to several events over the past four years: To what extent does political rhetoric, fake news and outlandish conspiracy theorizing contribute to attempted acts of violence?

Cheryl Paradis is a professor of psychology at Marymount Manhattan College in New York. She’s the author of the 2010 book “The Measure of Madness: Inside the Disturbed and Disturbing Criminal Mind,” and spoke with The Post by phone about how popular conversation and mental illness can combine in toxic ways.

Paradis was quick to reinforce that she couldn’t speculate on the mental illness of either Comello or Sayoc. She also noted, though, that it’s common for the mentally ill to “latch on to ideas that are salient to their time period.” Centuries ago, it was witches. More recently, alien abductions. Even more recently, she said, delusions center on things like the government putting implants in people’s bodies.

“This idea about QAnon and the deep state — for some people that have psychiatric illness, this is what the theme may be,” Paradis said.

Several years ago, the New Yorker looked at the “Truman Show delusion,” in which the mentally ill believe, like the protagonist of that movie, that they are the stars of a reality show that has being filmed 24 hours a day. But, she said, she doesn’t hear about that much anymore, because the movie isn’t as popular or common in the cultural conversation.

Politics is.

“What’s going on politically can galvanize, it can become a focus for people who have serious psychiatric illnesses,” Paradis added. “They could be susceptible, influenced by what’s going on in current events. This is a time in which many people are watching and very focused on the upcoming election, for example — and people have strong feelings about it. People that have psychiatric illnesses, just like anyone else, can be influenced by what’s going on in today’s political climate.”

The likelihood of carrying out an act of violence in response to delusions or schizophrenia is low. The “overwhelming majority” of people who have such illnesses aren't violent, despite portrayals in popular media. The type of illness, though, can make a difference.

“Research does show that of all the different types of delusions — for example, you could have grandiose delusions, you could think that you are the next messiah, Jesus Christ or you have special abilities — their likelihood of acting violently is very low,” she explained. “People, on the other hand, who have paranoid delusions, who feel that they are being attacked or that their life is being threatened or that someone they care about’s life is being threatened are at an increased risk.”

"But again,” Paradis added, “still such a low rate of violence. And that's what makes it impossible, very, very difficult to predict."

When Sayoc was arrested last year, authorities seized the van in which he had been living. It was plastered with images and messages lifted from Trump’s political rhetoric and included images of people Trump had disparaged by name, some of whom Sayoc had targeted with his bombs. Comello’s Instagram account similarly identified particular prominent officials, including Rep. Ilhan Omar (D-Minn.). It highlighted QAnon posts targeting Democrats more broadly.

That sort of isolation of individuals, Paradis said, is particularly troubling.

“Whenever people are identified as targets, it increases the likelihood that someone might act against them,” she said. “Again, someone with a psychiatric illness who has access to firearms, if they are being influenced by what they read and what they hear about with identified targets, it’s of concern.”

It doesn’t appear that Cali was ever targeted by QAnon. He certainly wasn’t a focus of Trump’s. Instead, a law enforcement official told reporters, Comello appears to have known Cali’s niece. Details of the shooting itself are still unclear, and the accuracy of his attorney’s presentation of events remains undetermined.

It remains fully possible, though, that mental illness caused Comello to believe fervently that QAnon was real and that the deep state encompassed people in positions of power on both sides of the law. That Comello saw the alleged mobster as dangerous to the country just as much as he saw de Blasio in that light. That this jumble of thoughts — the things he had read or seen and the shaky structure into which he had fit them — brought him to Cali’s house and led him to pull the trigger.

It’s fully possible that a similar chain of events affected Sayoc. The filing submitted by his attorneys note that, after Trump was elected, their client “passionately championed the President on social media and at rallies and covered his van with stickers supporting President Trump and criticizing his political opponents."

“Through these actions,” they write, “Mr. Sayoc found the sense of community that he had been missing for so many years.” By tracking Trump and conservative news media, he also, apparently, found named targets who he thought threatened that community.