A guard in a watchtower shot a “non-lethal” round at detainees inside Guantánamo prison’s $744,000 soccer field for cooperative captives earlier this year in the latest disclosure of simmering unrest at the Pentagon outpost in southeast Cuba.

The military on Tuesday acknowledged the Jan. 2 afternoon incident after The Miami Herald began assembling accounts from prison camp lawyers who were until recently prevented from describing their conversations with their captives.

“We are in danger. One of the soldiers fired on one of the brothers a month ago,” Yemeni prisoner Bashir al Marwaleah wrote in a letter received Feb. 22 by the New York law firm handling his unlawful detention suit.

In another account, dated Feb. 6, attorney Clive Stafford Smith wrote the admiral in charge of the prison camps seeking “a formal investigation” into the “use of firearm incident” at Camp 6. Stafford Smith said Tuesday he has not received a response.

Navy Capt. Robert Durand, the prison spokesman, said the watchtower guard correctly followed “crowd dispersal” procedures during the episode, which he called “a discrete incident that was over and done with.” He refused to specify what type of round was fired at the camp where about 100 of the 166 captives live in medium-security communal confinement — beyond calling it “one non-lethal round” similar to those “used by the Bureau of Prisons.”

Durand said no one was hurt. The lawyer said one prisoner “was injured in the throat.” While he did not name him, Stafford Smith described the wounded prisoner as an Afghan Taliban who had been identified in news reports as a potential candidate for release in Afghanistan peace talks.

According to the narrative emerging from both sides, a detainee in the recreation yard had sought the attention of a tower guard who controlled a gate leading to the pathway back to the prison. Durand said he tried to scale a fence, a violation of rules, but climbed down when the guard ordered him to do it.

Stafford Smith said he was told the guard “came out of the guardhouse in the tower, and aimed his rifle at the prisoner.”

Other detainees began to intervene, both sides said.. Durand said they threw rocks. The lawyer said “the guard swung his rifle around on them, and fired one round.” After “the use of non-lethal force,” the prison said in a statement, “the crowd immediately stopped throwing rocks and became compliant.”

The episode was exceptional because it was the first known gunfire response inside the camps with the possible exception of an episode in May 2006 when guards lobbed canisters of tear gas into a now defunct compound called Camp 4. Rubber bullets may also have been fired then, Durand said. In that episode, cooperative prisoners fought camp guards who charged inside a bunkhouse to quell unrest that lawyers subsequently said was fueled by rumors that guards would be seizing the captives’ Qurans.

Word has been slow to reach the public of the January episode, according to defense lawyers, because the Justice Department team that reviews attorneys’ notes and mail has been slow to release them.

In addition, several lawyers said, the detention center made it difficult for them to consult their clients in the aftermath of the shooting. Stafford Smith said he never got a response from the prison camps commander, Navy Rear Adm. John Smith Jr., to his Feb. 6 request for a formal investigation. Durand said the lawyers had no authority to write the military and were obliged to request the investigation of the Department of Justice, where spokesman Dean Boyd said it was purely a military question.