In 2016, the 45-year-old was the first to report on a meeting between former US president Bill Clinton and then-attorney general Loretta Lynch during an investigation into Hillary’s Clinton’s use of a private email sever as secretary of state.
Ms Clinton’s emails became a focus for Mr Trump, who defeated the 2016 Democratic presidential nominee on the back of nicknames including “Crooked Hillary”.
Shortly after Mr Trump Jr’s Instagram story on Sunday, Republican congresswoman Ms Boebert also wrongly theorised about Mr Sign’s death, in a tweet.
She shared a clip of the former Alabama journalist in 2019 telling Fox News that his family had received threats for reporting on the Clintons and the 2016 nominee’s emails.
Ms Boebert wrote : “Why is it that so many who cross the Clinton Crime Syndicate end up dead?”
Mr Sign, who was found dead at home in Hoover, Alabama, told Fox News during the interview that he had been threatened following his 2016 story on Ms Clinton, the former US secretary of state.
"My family received significant death threats shortly after breaking this story,” said the journalist. “That's why I came back to WBMA ABC 33/40 in Birmingham [from KNXV-TV in Phoenix].”
It is not the first time Ms Boebert has alluded to a conspiracy in the style of QAnon, which theorises that Democrats and a world elite are running a sex trafficking ring — with its so called members, including Ms Clinton, supposedly facing arrest or a day of reckoning.
The congresswoman, asked in February if Democrats and Ms Clinton will be arrested, allegedly told the Delta County Independent; “I believe we will see resignations begin to take place”.
Ms Clinton herself recently said of the false theories: "It's hurtful. I'll be really honest with you. It's hurtful not just to me and my family, but to my friends and other people to know that this is not just false, but sometimes painfully false."
On Twitter, dozens of critics of both Mr Trump Jr and Ms Boebert condemned the allegations about Mr Sign’s death, with one writing: “That’s a great question. Why is it so many Trump allies end up in prison?”
“When the GQP runs out of things to say they huddle up and decide there’s more baseless allegations for the Clintons they can hurl out there,” wrote another Twitter user. “It’s not a political platform. It’s a vendetta.”
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