The majority of more than 140,000 tips sent to the FBI about the attack have come from friends and family of those involved A mob of Trump supporters breach the US Capitol on 6 January 2021. Photograph: Carol Guzy/ZUMA Wire/REX/Shutterstock Sign up for the Guardian Today US newsletter When Alison Lopez discovered her uncle’s sister had been part of the mob that breached the Capitol doors on 6 January, she immediately reported her to the FBI. “I had no second thoughts,” she said. Lopez found out about her in-law’s participation when the woman in question called her aunt from inside the Capitol to brag about “taking back the election”. Lopez, who is 42, said she had known the relative her whole life but had “no qualms” about reporting her. “If I saw my grandmother making bombs in her basement, or my aunt breaking into a home, I would have to intervene as well – it’s just about doing what’s right,” she said. In the week after the attacks on the Capitol, there has been a concerted effort to “unmask” rioters online, with self-styled detectives investigating who’s who in videos and photos posted from the attack. Outing family members – either online or to authorities – has marked a new frontier of the rift Trumpism has created in the US. Lopez said she was horrified but not surprised to see a loved one participate in the riot. Over the last four years she has watched helplessly as members of her family became increasingly entrenched in the world of hateful rightwing conspiracy theories. “These are people who never really identified with politics before, and now they have just let this consume their lives,” Lopez said, adding she does not consider herself a Democrat and has voted for Republican candidates in the past. If I saw my grandmother making bombs in her basement ... I would have to intervene as well – it’s about doing what’s right Alison Lopez More than 140,000 people have sent tips to the FBI reporting participants in the riots on the Capitol on 6 January, resulting in at least 200 arrests. The vast majority of those, according to the Department of Justice, come from friends, family, and other acquaintances of those involved in the attacks. The Massachusetts teen Helena Duke received a flood of support this week when she posted a video outing her own mother, aunt and uncle as having attended the Capitol protests. The 18-year-old said her mother, who appears to be harassing a Black woman in the video shared, previously condemned her for attending Black Lives Matter protests. “If I did nothing, I felt I was as bad as them,” Duke told Good Morning America. The decision to report a family member or publicly out them as espousing dangerous views can make a huge impact in stopping the spread of hate speech, said Talia Lavin, an expert in extremism and white supremacist groups and the author of Culture Warlords. “I applaud the bravery of people who have called out people in their own families for this kind of radicalization,” she said. “When people experience ostracization or disavowal from one’s own family, it can lead to a kind of cooling of extremist sentiment, because individuals are for the very first time experiencing a consequence for what they have so proudly engaged in for so long.” Online sleuthing is not new, especially among hate speech and extremism investigators, who have for years hunted down and outed racists and fascist agitators to employers in hopes to foster accountability. But in the aftermath of the insurrection, the practice has gone more mainstream, with journalists, activists and the FBI tweeting out photos and videos of the riot and encouraging followers to investigate them. Online sleuthing has its drawbacks: a Chicago firefighter faced harassment after being falsely identified as the killer of a Capitol police officer through a blurry video image. Another photo was falsely traced to a man pictured on an Antifa website, a tie that has been definitively disproven. But the chance of mistaken identity is much lower when the accusation comes from a family member or loved one. Leslie, a woman in Chicago who asked that her last name not be used in this story, said she and her sister both submitted screenshots of images their mother posted on social media from the steps of the Capitol during the riots to the FBI. More than 140,000 people have sent tips to the FBI reporting participants in the riots on the Capitol on 6 January. Photograph: Michael Nigro/Pacific Press/REX/Shutterstock Leslie, who considers herself far left politically, said she had watched in horror as vigilantes stormed the Capitol on 6 January, only to learn days later her estranged mother was one of them. “I almost passed out,” she said of the moment she saw the images. “I was really shocked, she was on the scaffolding we saw people climbing on TV. It was such a helpless, horrifying feeling.” Leslie said she and her three siblings all stopped speaking to their parents after they got sucked into QAnon, movement surrounding a disproven conspiracy theory that Donald Trump is saving the world from a secret cabal of child abusers. She said she watched her evangelical mother go from being a devout Christian to posting hate speech on Facebook and aligning herself with the far right. “I am really, really angry that I have essentially lost my family to a cult,” she said. “I am angry that people were not taking the rise of QAnon more seriously. People kept saying, ‘nobody is actually going to do anything, it is just a bunch of idiots online’.” “Well, the people at the Capitol are the people who were looking at this online,” she said. “This is what happens when you don’t do anything.” Leslie is not alone: support groups have emerged in recent years for the countless Americans who have lost loved ones to the conspiracy theory. Leslie said she is hoping a call from the FBI could serve as “kind of wake up call for them”, she said. “Maybe if she gets a call from the authorities she will realize this is not just a game, this is not just something playing out on Facebook. This is real and people got killed,” she said.