Sulaimon Brown, the former mayoral candidate who said he was paid and promised a city job by Mayor Vincent C. Gray’s campaign, thanked federal investigators for their “hard work” Wednesday — a day after a friend of the mayor pleaded guilty to providing funds to Brown and destroying the evidence that showed a record of the payments.

“I was not looking for vindication for truth need not be vindicated,” Brown released a statement by e-mail. “I was seeking justice.”

He also said, “Mayor Gray should resign immediately if not sooner for his violation of not only me, but the Public trust of The District of Columbia residents.”

In March 2011, The Washington Post published a story about Brown’s allegations that he was paid to stay in the 2010 mayoral Democratic primary race to disparage then-Mayor Adrian M. Fenty.

Gray has repeatedly denied knowing about any payments.

Thomas W. Gore, a longtime Gray friend and assistant treasurer of his 2010 mayoral campaign, pleaded guilty Tuesday to a felony count of obstruction of justice for shredding a spiral notebook that prosecutors have said contained a record of the payments. He also pleaded guilty to three misdemeanor counts of making a contribution in someone else’s name.

Brown’s allegations against the mayor’s campaign have led to a broadening federal investigation into funding of D.C. political campaigns.