Washington (CNN) -- A suburban Washington county official at the center of an FBI investigation into years of kickbacks says he is innocent and that the facts will prove it.

Jack Johnson, who served as the executive of Prince George's County, Maryland, since 2002, spoke to reporters late Friday after the FBI released details of how he and his wife allegedly tried to hide checks and evidence of illegal payments, even going so far as to flush a $100,000 check down the toilet.

The Johnsons were both charged with tampering with evidence and destruction of records after they appeared in federal court late Friday in Greenbelt, Maryland, just outside the U.S. capital.

"I'm innocent of these charges and I just can't wait for the facts to come out," said Johnson. "When they come out, I am absolutely convinced that I'm going to be -- that we will be vindicated."

An affidavit by an FBI investigator whose team was monitoring wiretaps detailed a dramatic end to an alleged years-long kickback scheme organized by the couple.

After the Johnsons were arrested, FBI agents searched their Mitchellville, Maryland, home, walking out with at least 10 boxes filled with evidence. U.S. Attorney Rod Rosenstein stressed the investigation is continuing.

The Johnsons were released on their own recognizance, but Jack Johnson will be required to wear a monitoring device and presumably will be allowed to continue serving out the last weeks of his expiring term as county executive if he chooses. The judge, however, ordered him not to attempt to destroy any evidence.

Jack Johnson had been the Prince George's County prosecutor prior to his eight years as executive.

Leslie Johnson was just recently elected to the nine-member Prince George's County Council.

"We socialize with them and it's just shocking," a female neighbor of the Johnsons told CNN affiliate WUSA on Friday. "They're very nice people, very kind people."

The 10-page affidavit says the FBI began investigating Johnson in 2006 when it learned that certain real estate developers were paying Johnson for contracts. That led to "a series of authorizations for the interception of wire communications."

The frantic end began early Friday when Johnson allegedly received a $15,000 payoff, and the FBI suddenly barged into the room to demand an explanation.

Johnson told them the cash was for a party marking the end of his tenure as county executive. He also claimed he had no dealings with the developer who was with him.

The FBI says Johnson made a series of false statements. The agents let him go but then eavesdropped on a series of frantic phone calls between the couple as Jack Johnson and the FBI headed for the Johnsons' Mitchellville home.

"Two women (agents) are at the door," Leslie told her husband.

"Don't answer it," Jack said. He told her to run upstairs to their bedroom and go to "my drawer."

"You will see a check in there that (an unidentified developer) wrote to me," he said.

The affidavit says that when Leslie found the check, Jack told her to tear it up. "Do you want me to put it down the toilet?" she asked. Jack Johnson replied, "Yes, flush that." The agents monitoring the phone calls heard a flushing sound.

Leslie Johnson grabbed cash from the bedroom and also ran to the basement and grabbed more cash. "Put in your bra and walk out or something, I don't know what to do," Jack Johnson said.

"I have it in my bra," his wife replied.

Agents then searched Leslie Johnson and found $79,600 in her underwear, the FBI affidavit says.

The wild ending may end up costing the Johnsons. The FBI says there is probable cause to believe that the pair "tampered with ... evidence and engaged in destruction, alteration, and falsification of records in a federal investigation."

The FBI document does not say how much money Johnson may have received in kickbacks or bribes. It does say at least some of the funds involved were targeted from an $80 million budget for programs supported by federal grants such as those from Department of Housing and Community Development.

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