Updated: 17 MAY 21 13:51 ET

By David Shortell, Jeremy Herb, Paula Reid and Devan Cole, CNN

(CNN) -- Joel Greenberg, a former Florida tax collector and close confidant of Florida Republican Rep. Matt Gaetz, formally pleaded guilty on Monday morning to six federal charges in a court hearing, admitting to a federal judge that he had knowingly solicited and paid a minor for sex.

Greenberg spoke sparingly throughout the 45-minute hearing and with a tone of dejection, responding "yes" and "I do" as the judge read the details of his plea agreement. He wore a dark jumpsuit and had his hands shackled in front of him.

The guilty plea from Greenberg, a former Seminole County, Florida, tax commissioner, comes after he struck a deal with federal prosecutors to avoid some of the other 33 federal charges he had faced that ranged from identity theft to fraud and bribery allegations.

As part of the plea, Greenberg has agreed to give "substantial assistance" to prosecutors as part of their sprawling investigation, including by testifying at trials or in federal grand juries if needed and in turning over all documents he might have that could help the federal inquiry.

Federal investigators are still examining whether Gaetz broke federal sex trafficking, prostitution and public corruption laws and whether he had sex with a minor. Gaetz has not been charged and denies any wrongdoing.

Previously, CNN reported that Greenberg had been providing information to investigators about how he and Gaetz had encounters with women who were given cash or gifts in exchange for sex.

The Greenberg plea documents released Friday document how he used popular cellphone apps to make contacts, paid thousands of dollars for sex with younger women, had drug-laced, multi-person rendezvous at hotels and repeatedly took advantage of his public office's power and financial coffers.

Gaetz isn't mentioned in the 86 pages of plea deal documents released last Friday, which his spokesman, Harlan Hill, pointed to on Friday in a statement responding to the plea agreement.

"Joel Greenberg has now confessed to falsely accusing an innocent man of having sex with a minor," Hill said in a statement on Monday.

In the plea agreement, Greenberg admitted to falsely accusing a Florida teacher of having sex with a student in 2019. Greenberg allegedly targeted the teacher after he filed paperwork to oppose Greenberg for county tax collector.

Greenberg's admitted sex charge carries a mandatory minimum sentence of 10 years in prison, yet prosecutors in the plea deal said that if he helped them significantly, he may be able get a sentence less than the minimum.

Speaking to reporters after the hearing, Greenberg's attorney Fritz Scheller said that his client felt a "great deal of remorse."

"He's on the path towards rehabilitation and he has a great deal of remorse," Scheller said. "I think he's feeling a sense of acceptance."

Scheller would not say how many times Greenberg has met with federal investigators and declined to comment on the plea's potential consequences for Gaetz and other public officials in Florida.

"Does my client have information that could hurt an elected official? I guess this is must-see television. You'll just have to wait and see," Scheller said.

Scheller declined to respond to the statement from Gaetz's spokesman when it was read to him on Monday.

Greenberg's cooperation with the government was briefly addressed in the hearing. Judge Leslie Hoffman told Greenberg how his cooperation could potentially impact his final sentence, and Greenberg acknowledged that he understood.

As part of the agreement, Greenberg also pleaded guilty to charges of fraud and stalking a political rival. He will have to register as a sex offender and pay restitution to the minor victim.

Roger Handberg, the prosecutor handling the case, told the court that the plea agreement discussed Monday was the entirety of the agreement -- no portion of the agreement remained under seal and out of the public eye.

Brian Beute, the former competitor of Greenberg's for the tax collector seat whom Greenberg admitted to harassing Monday, told reporters ahead of the hearing that he was satisfied with the plea agreement.

"I have a renewed hope and satisfaction with our federal system," Beute said.

This story has been updated with additional developments and reaction.