The former Capitol Hill staffer has been linked to Gaetz since at least the summer of 2017 - a time period of interest for investigators.
"I would not feel really comfortable if I was anyone that had committed a crime with" Joel Greenberg right now, one former FBI agent told Insider.
The Justice Department is investigating whether Rep. Matt Gaetz, a Florida Republican. violated federal sex trafficking laws.
Greenberg pleaded guilty to six felony counts including sex trafficking and agreed to cooperate with prosecutors.
Greenberg's plea deal has been widely anticipated, and he's already provided prosecutors with information on an "array of topics."
At an Ohio event, Gaetz denied accusations that he exchanged money for "naughty favors" - and instead called out "earmarks" for being corrupt acts.
The news comes hours after Insider reported Joel Greenberg, a former Gaetz wingman, will plead guilty to six felony counts on Monday.
Greenberg's cooperation with prosecutors opens the possibility of a nightmare scenario for Rep. Matt Gaetz of Florida.
It's a significant development and one that will likely help prosecutors tighten the screws on Gaetz as they investigate whether he broke sex-trafficking laws.
The Daily Beast interviewed women who discussed their experiences with Greenberg, a former Florida tax official.
The letter is the most damning evidence to date against Gaetz as the Justice Department investigates whether he broke sex-trafficking laws.
The Daily Beast reported payments Greenberg made to women had labels that included "Ass," "Stuff," or just a lipstick kiss emoji.
Greenberg's cooperation could be crucial to helping prosecutors determine Gaetz's intent in the conduct he's accused of engaging in.
Greenberg, who is facing 33 federal charges, including sex trafficking of a minor, could be key in the DOJ's investigation into Gaetz.
Greenberg, who faces 33 federal charges, is an associate of Rep. Matt Gaetz and a key player in the federal investigation into the congressman.
The Florida Republican sent the money to Joel Greenberg in May 2018 over Venmo, The Daily Beast reported.
Greenberg and Gaetz are the focus of a wide-ranging DOJ investigation into whether they broke federal sex trafficking laws.