The chairman of the Joint Chiefs of Staff vowed Tuesday to get to the bottom of charges that a former soldier raped and killed a young Iraqi woman and shot her family to death. Three other soldiers still in Iraq are suspected of joining in the crime and helping cover it up.

"Any such acts on the part of a U.S. servicemember, if proven to be true, are totally unacceptable. We know that in uniform, and our fellow citizens know that," Marine Gen. Peter Pace said Tuesday.

"If there are those who have done things as they have been accused of, we will get to the bottom of it. We will do the investigations, we will find out what the truth is and if necessary we will take those who deserve to be taken to court so they can have their day in court," he told NBC's "Today" show.

Click here to read the charges against the former U.S. Army soldier (pdf).

The military had at first blamed insurgents when the four bodies were found in March inside a burned house near Mahmoudiya, south of Baghdad.

But on Monday, federal prosecutors revealed the outcome of a joint military and FBI investigation: They now believe U.S. soldiers who manned a checkpoint a short distance from the home plotted the attack and tried to cover it up.

Prosecutors charged one, Steven D. Green, a 21-year-old former private who was honorably discharged this spring by the Army because of a "personality disorder." He was charged Monday with rape and four counts of murder during an appearance in a federal courtroom in Charlotte.

Wearing baggy shorts, flip-flops and a Johnny Cash T-shirt, Green spoke only to confirm his identity and stared as a federal magistrate ordered him held without bond on murder and rape charges that carry a possible death penalty.

His father, John Green, told The Associated Press at his home in Midland, Texas, Tuesday morning that he declined to comment on the case, on the advice of his attorney.

According to a federal affidavit, Steven Green and three other soldiers from the Fort Campbell, Ky.-based 101st Airborne Division had talked about raping the young woman, whom they first saw while working at a traffic checkpoint near her home.

On the day of the attack, the document said, Green and other soldiers drank alcohol and changed out of their uniforms to avoid detection before going to the woman's house, with Green using a brown T-shirt to cover his face.

Once there, the affidavit said, Green took three members of the family — an adult male and female, and a girl estimated to be 5 years old — into a bedroom. Shots were heard.

"Green came to the bedroom door and told everyone, 'I just killed them. All are dead,"' the affidavit said.

The affidavit is based on FBI and military investigators' interviews with three unidentified soldiers assigned to Green's platoon. Two of the soldiers said they witnessed another soldier and Green rape the woman.

"After the rape, (the soldier) witnessed Green shoot the woman in the head two to three times," the affidavit said.

One of the three soldiers interviewed said he was left behind to mind the radio at the traffic checkpoint. That soldier said Green and three others returned from the woman's house "with blood on their clothes, which they burned. Immediately after this, they each told (the soldier) that this is never to be discussed again."

An official familiar with details of the investigation in Iraq told The Associated Press that a flammable liquid was used to burn the rape victim's body in an apparent cover-up attempt.

The affidavit noted that prosecutors have photos taken by Army investigators in Iraq of all four bodies found inside a burned house and a photo of a burned body of "what appears to be a woman with blankets thrown over her upper torso."

The age of the young woman was unclear. FBI documents estimated her age to be 25, but a neighbor of the family said the rape victim was 14 and her sister was 10. The Washington Post reported the rape victim was 15 and that her mother worried her daughter had attracted the attention of U.S. soldiers at a checkpoint.

Green, who was arrested Friday in the town of Marion northwest of Charlotte, is being prosecuted in federal court rather than military court because he is no longer in the Army. According to the affidavit, he was discharged after 11 months and "before this incident came to light."

The soldiers accused in the rape and killings are from the same platoon as two soldiers whose mutilated bodies were found June 19, three days after they were abducted by insurgents near Youssifiyah, southwest of Baghdad. Military officials say they believe guilt over the mutilations may have spurred a confession by one of the soldiers during a combat-stress debriefing late last month.

No other soldier has been charged in the case, said Maj. Joseph Breasseale, a U.S. military spokesman in Baghdad. However, military officials have said four Army soldiers have had their weapons taken away and were being confined to their base near Mahmoudiya.

The mayor of Mahmoudiya, Mouayad Fadhil, said Monday that Iraqi authorities had started their own investigation. He said U.S. Army officers were also seeking permission to exhume one of the bodies; the U.S. military declined to comment on the report because the investigation is ongoing.

According to the affidavit, Green was arrested while traveling back to Fort Campbell after attending a funeral for one of the mutilated soldiers in Arlington, Va.

Court officials said Green will have a preliminary hearing and a detention hearing on July 10 in Charlotte, and will then be brought to Louisville.

He was quoted in December by the Fort Campbell Courier about a search for insurgents and expressed surprise at the ease of the mission.

"I was surprised by how many people weren't home, but the ones who were there were submissive and let us look through their things," he said then.