A man armed with an AR-15 is killed in a shootout after he tried to break into the FBI offices in Cincinnati. A Pennsylvania man is arrested after posting death threats against agents on social media. In cyberspace, calls for armed uprisings and civil war are growing. This could be just the beginning, federal authorities and private extremism monitors warn. A growing number of fervent supporters of Donald Trump appear poised to fight back against the FBI or others they believe are overreaching in their investigation of the former president. Law enforcement officials across the country are warning and warning of an increase in threats and the possibility of violent attacks on federal agents or buildings in the wake of the FBI’s investigation into Trump’s Mar-a-Lago home. Experts who study radicalization and online disinformation — such as Trump’s aggressive false claims of a stolen election — note that the recent surge was sparked by a legal search of Trump’s Florida home. What can happen in the event of arrests or charges? “When the messages get to a certain pitch, things start happening in the real world,” said former New Jersey Attorney General John Farmer, a onetime federal prosecutor who now directs the Eagleton Policy Institute at Rutgers University. “And when people in positions of power and public trust start echoing extremist rhetoric, we’re even more likely to see real-world consequences.” Fueled by the right-wing media, Trump and his allies’ angry claims about the investigation are fueling his supporters’ mistrust of the FBI — though it is run by a Trump appointee — and the federal government more generally. And at least some of Trump’s supporters now seem to be acting on his anger. Last week, a man wearing body armor and armed with a handgun and a nail gun attempted to break into the FBI office in Cincinnati. He was later shot and killed by police after an exchange of fire with officers. Authorities say they believe the man had posted dark messages on Truth Social, Trump’s online platform, including one that said federal agents should be killed on sight. Another man drove his car into a U.S. Capitol barricade Sunday and began shooting into the air before fatally shooting himself. On Monday, the Justice Department announced the arrest of a Pennsylvania man who had made repeated threats against the lives of FBI agents on Gab, a platform popular with Trump supporters. “You declared war on us and now it’s open season on YOU,” he wrote in a post shared by authorities. A joint intelligence bulletin from the FBI and Homeland Security warns of an increase in violent online threats targeting federal officials and government facilities. These include “a threat to plant a so-called dirty bomb in front of FBI headquarters,” along with calls for “civil war” and “rebellion,” according to a copy of the document obtained by The Associated Press. Reports of a “civil war” on platforms such as Facebook and Twitter increased tenfold in the hours immediately following last week’s investigation at Mar-a-Lago, according to analysis by Zignal Labs, a company that analyzes social media content. . Many of the posts contained unsubstantiated claims suggesting that President Joe Biden ordered the FBI to search Trump’s home or that the FBI planted evidence to incriminate Trump. “For Biden to send the FBI to raid a former president, Mr. Donald Trump’s home, is a declaration of WAR against him and his supporters,” wrote one poster on the Telegram platform. The briefing also noted that federal law enforcement officials have identified multiple threats against government officials involved in the Mar-a-Lago investigation, including calls to kill the judge who signed the search warrant. The names and home addresses of FBI agents and other officials have been posted online, along with references to family members who could be additional targets, according to the intelligence documents. The threats are ominously similar to the online rhetoric that preceded the Jan. 6, 2021 attack on the U.S. Capitol, says Rep. Bennie Thompson, D-Mississippi, who chairs the House Jan. 6 and Homeland Security Committee. “These threats of violence and even civil war — mostly coming from far-right extremists on the Internet — are not only un-American, they are a threat to our democracy and the rule of law,” Thompson said. The search of Trump’s residence was based on a legal warrant signed by a judge. But that’s beside the point for Trump and his allies. “This is an attack on a political opponent on a scale never before seen in our country,” Trump wrote Monday in a post on Truth Social. “Third World!” Republican Rep. Paul Gosar of Arizona called the investigation “tyranny” and tweeted: “We must destroy the FBI.” Another Arizona congressman, Republican Andy Biggs, tried to shift some of the blame to the individual agents who conducted the investigation. “This looked more like something you would see in the former Soviet Union,” Biggs said this week. “Why did all these agents go on purpose?” Republican Sen. John Thune told reporters in Sioux Falls, South Dakota, on Tuesday that while the Justice Department has shown it followed legal protocols in obtaining the search warrant, its reticence about the Trump probe has left people questioning the motivations of law enforcement. “There are just a lot of unanswered questions that, left open, create a lot of suspicion among the American people, and the one thing you don’t want is for people to distrust law enforcement,” Thune said. Other Republicans tried to tone down the rhetoric, as did Arkansas Gov. Asa Hutchinson during a weekend appearance on CNN. “We have to step back from judging them,” Hutchinson said of the agents. “The FBI is simply carrying out its responsibilities under the law.” But much of the conservative media has not heeded that advice. “The Mar-a-Lago raid was not an act of law enforcement, it was the opposite,” Tucker Carlson said on his Fox News show Monday night. “It was an attack on the rule of law.” Fox also shared an edited photo that falsely depicted the judge who signed the warrant receiving a foot massage from Ghislaine Maxwell. Maxwell was sentenced in June to 20 years in prison for helping her friend Jeffrey Epstein molest underage girls. The original photo was not of the judge but of Epstein, who killed himself in 2019 while awaiting trial. Fox News’ Brian Kilmeade later said the harsh image was shared as a joke. Republican anger at the FBI has its roots in the 2016 election and investigations into the Trump campaign’s alleged ties to Russia and Hillary Clinton’s handling of classified material in a private email account. That anger has only grown as new investigations focus on Trump, his efforts to overturn the 2020 election and his handling of classified material since leaving office. Unsubstantiated claims that the FBI was secretly framing Trump supporters for their violent actions on January 6 also drew ire from conservative social media users. “Well you guys started this civil war,” wrote one Gab poster “And others will surely finish it for you.” —— Associated Press writers Michael Balsamo and Stephen Groves contributed to this report.