Before joining the State Department in 2017, Klein worked for the Trump campaign, which paid him a $15,000 salary.
The alleged presence of a Trump political appointee at the riot may tie those events more closely to the president, although there is already ample evidence that many of those charged were inspired by Trump's false claims about widespread election fraud and by his call for supporters to descend on Washington on January 6 for events that he promised would be "wild".
A Department of State diplomatic security special agent interviewed by an Federal Bureau of Investigation agent said that Klein worked in the Office of Brazilian and Southern Cone Affairs, according to the court papers.
Politico's Josh Gerstein reached Klein's mother, Cecelia Klein, by telephone Thursday evening, and she said that she and her son had differing political views and therefore usually abstained from discussing political topics, but he had confirmed that he had been in the area that day. Before his appointment, he was a member of Trump's 2016 presidential campaign. He held a top secret security clearance that was renewed in 2019, according to the court papers.
Klein was caught as part of the FBI's efforts to spread photos of the insurrectionists on social media and hope for tips. He also worked at the conservative advocacy organization, Family Research Council, which lobbies against pornography, abortion, divorce, and LGBT rights.
Authorities say Klein pushed toward the doors and "physically and verbally engaged" with officers trying to keep the mob back.
Body camera and open-source footage captured Klein violently shoving a riot shield taken from an officer and "inciting the mob" - including by calling for "fresh people" at the front of the crowd - in his attempts to breach the police line.
"I'm wondering if there's a place I could stay in detention where I don't have cockroaches crawling over me while I'm trying to sleep", Klein told the judge. The exact charges against Klein have not yet been made public.
"Fred's politics burn a little hot", she said, "but I've never known him to violate the law".
Klein faces charges for unlawful entry with intent to disrupt government business and for engaging in physical violence; disorderly conduct with intent disrupt Congress; obstruction of an official proceeding; obstructing or interfering with law enforcement in the course of their official duties and during civil disorder; assaulting police while using a deadly or risky weapon.