Former District of Columbia and mayoral candidate Sulaimon Brown provided damaging testimony against D.C. Mayor Vincent Gray on Monday at a city council hearing about the Gray administration’s hiring practices. Brown has alleged that two people who worked on Gray’s mayoral campaign paid him to criticize then-Mayor Adrian M. Fenty, whom Gray defeated during last year’s race, and also guaranteed him a job in Gray’s administration.

“The mayor is a crook,” said Brown, who was fired in February from a $110,000-a-year job as an analyst in the city’s Department of Health Finance, the Washington Post reports. “Everyone knows you’re running a sham.”

In April, Brown refused to testify and fled a hearing at which he was scheduled to address the council, but on Monday he had copies of money orders that are part of the alleged pay-offs that totaled $650 and said that he’d also received an “unknown amount of cash.”

According to Brown, Gray invited him to step outside during a fundraiser last year and “while we were outside, he thanked me.” Gray also then allegedly pointed him to campaign consultant Howard L. Brooks, and said, ”I think Howard has something for you.” Brooks then handed him money, Brown testified.

He also said that in a conversation with Gray at an inauguration event about the position he was allegedly promised, the new mayor told him, “You’ve got the job. Don’t [expletive] it up,” the Post reports.

Brown insisted on wearing mirrored sunglasses during the hearing, was frequently combative and refused to answer questions that he felt would implicate him. He also refused to give copies of the money orders to the council, but did share them with reporters covering the hearing. He has been ordered to turn them over to the committee overseeing the matter by June 15.

The mayor’s office declined to comment on Brown’s allegations but may not be able to remain silent for long. The case has prompted an investigation by the U.S. attorney’s office, the FBI and a congressional committee.