A few months after turning 17 — and two years before he was arrested — Vincent Vetromile recast himself as an online revolutionary.

Offline, in this Rochester, New York suburb, Vetromile was studying heating and air conditioning at a community college. He spent hours with his father, working on cars.

On social media, though, the teenager spoke about reclaiming "our nation at any cost." Eventually he subbed out the grinning selfie in his Twitter profile with the image of a colonial militiaman shouldering an AR-15 rifle. And he traded his name for a handle: "Standing on the Edge."

In 2016, he sent the first of more than 70 replies to tweets from a fiery account with 140,000 followers, run by a man calling himself Donald Trump's biggest Canadian supporter. The final exchange came last December.

"Muslim No-Go Zones Are Springing Up Across America. Lock and load America!" the Canadian tweeted, with a map showing states with Muslim enclaves — including New York.

"If there were specific locations like 'north of X street in the town of Y, in the state of Z' we could go there and do something about it," Vetromile replied.

Weeks later, when police charged Vetromile and three friends with plotting to attack the Muslim settlement of Islamberg in Delaware County, New York, it raised questions about ideology and young people — and technology's role in bringing them together.

"I don't know where the exposure came from, if they were exposed to it from other kids at school, through social media," said Matthew Schwartz, the assistant district attorney prosecuting the case. "I have no idea if their parents subscribe to any of these ideologies."

Accused with 19-year-old Vetromile are Brian Colaneri, 20; Andrew Crysel, 18; and a 16-year-old The Associated Press isn't naming because of his age. They've all pleaded not guilty. Parents or other relatives declined comment. Their attorneys did not return calls; in court some of them have chalked all this up to talk among buddies.

There is no indication the four had set a date for an attack, prosecutors say, and reports they had 23 guns are misleading; the weapons belonged to family members. Prosecutors allege the suspects discussed using those guns and explosive devices against Islamberg, where residents have faced harassment by right-wing activists who call the community a terrorist training camp. A Tennessee man was convicted in 2017 of plotting to burn Islamberg's mosque.

Well beyond New York, the spread of extremism — and technology's role — has sparked concern. A House committee questioned Google and Facebook executives recently about their platforms' role in feeding hate crime. Experts point to algorithms used by search engines and social networks to prioritize content.

"Once you indicate an inclination, the machine learns," said Jessie Daniels, a professor at New York's Hunter College. "That's exactly what's happening on all these platforms ... and it just sends some people down a terrible rabbit hole."

There are few clues so far to explain how four with little experience beyond their high school years might have come up with the idea to attack Islamberg. What is clear, though, is the long thread of frustration in Vetromile's online posts.

Where once those posts centered around video games and English class, by 2017, Vetromile was directing strong statements at Muslims. The Canadian account, belonging to one Mike Allen, seemed to push that button.

When Allen tweeted, "Czech politicians vote to let citizens carry guns, shoot Muslim terrorists on sight," Vetromile responded: "We need this here!"

The December tweet about Muslim "no-go zones" included a video interview with Martin Mawyer, whose Christian Action Network made a 2009 documentary alleging Islamberg and other settlements were terrorist training camps. Police have said Islamberg does not threaten violence.

Online, Vetromile expressed concern that the video referred to "'upstate NY and California' and that's too big of an area to search for terrorists." When others chimed in, suggesting locations, Vetromile replied: "Worth a look. Thanks."

Months earlier, prosecutors say, the four suspects had started using an online messaging platform to discuss weapons and how they would use them in an attack. It's alleged that Vetromile set up the channel. In November, the conversation expanded to a second channel: "#militia-soldiers-wanted."

In January, the 16-year-old showed a photo to a classmate of one of his fellow suspects, wearing some kind of tactical vest, and said something like: "'He looks like the next school shooter, doesn't he?" according to local police. The other student reported the incident, leading to the charges of conspiracy to commit terrorism.

The allegations have jarred a region where political differences are the norm. Bob Lonsberry, a conservative talk radio host in Rochester, said he checked Twitter to confirm Vetromile didn't follow his feed. But looking at the accounts Vetromile did follow convinced him that politics on social media had crossed a dangerous line.

The alleged plot is an aberration, Lonsberry said. "But ... aberrations, like a cancer, pop up for a reason."

Mike Allen, the Canadian whose tweets Vetromile followed so closely, expressed dismay when an Associated Press reporter told him one of those accused in the plot had closely followed his feed. "And they got caught? Good," said Allen, 69, a retired real estate executive. "We're not supposed to go around shooting people we don't like."

The next day, Allen shut down his account — and his narrative all but vanished.

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AP investigative researcher Randy Herschaft in New York contributed to this story.