One of five prison guards charged in a sex-for-contraband scandal that ended in a deadly shootout with federal agents pleaded guilty Thursday to conspiracy to commit mail fraud.

Alfred Barnes, 42, of Thomasville, Ga., agreed to cooperate in the prosecution of other defendants. In exchange, the government dropped charges including witness tampering, bribery and mail fraud.

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The five men are accused of taking part in an alleged scheme in which guards reportedly paid female inmates for sex with alcohol, food, money and marijuana over a two-year period. The guards also were accused of intimidating inmates and witnesses to ensure their silence.

Authorities said prison guard Ralph Hill smuggled a gun into the Tallahassee Federal Correctional Institution on June 21 and opened fire when FBI and Justice Department agents arrived to arrest him and the other defendants.

Hill and Justice Department special agent William "Buddy" Sentner were killed. A prison employee assisting in the arrests was wounded. None of the surviving guards were charged in connection with the shooting.

Barnes testified that families of three female inmates mailed money orders to him and he provided them with cosmetics, jewelry, cigarettes and other tobacco products that he smuggled into the prison. He said he had sexual relationships with two of the women, and "basically just a money relationship" with the third.

Another guard, Vincent Johnson, also pleaded guilty Sept. 6 to conspiring to commit mail fraud in a similar deal with prosecutors. Johnson was not accused of having sex with inmates. Instead, coerced inmates to keep quiet about the scheme and to not cooperate with investigators, according to a statement of fact he signed.

Barnes and Johnson each could face a maximum sentence of 20 years in prison and $250,000 fine. Johnson's sentencing is set for Nov. 17 and Barnes' for Dec. 14.

Trial is scheduled to begin Oct. 30 for the other three guards, Gregory Dixon, Alan Moore and E. Lavon Spence.