The military has formally charged two Navy SEALs and two special-forces Marines in one of the most grisly cases of fratricide in recent U.S. history, The Daily Beast has learned.

Two members of elite SEAL Team Six, Petty Officer Anthony E. DeDolph and Chief Petty Officer Adam C. Matthews, along with two Marine Raiders face charges that include felony murder, conspiracy, obstruction of justice, burglary, hazing, and involuntary manslaughter in the strangulation death of a Green Beret, Army Staff Sgt. Logan Melgar. All four were charged with felony murder and with lying to investigators.

The charges were proffered against the four on Wednesday, according to the Navy. A preliminary hearing in military court is scheduled for December 10.

Melgar, assigned to the 3rd Special Forces Group, was killed in the West African nation of Mali in June 2017, as first reported by the New York Times.

The Marine Raiders’ names have not been made public. All four names are redacted to the public on the formal charge sheet.

According to the charges, the alleged conspirators “drove to the Marine quarters” in Bamako, Mali “to obtain duct tape,” then drove to the shared Army/Navy headquarters, “entered the bedroom of SSG Melgar by breaking through his locked door,” restrained him with the duct tape, and “strangled SSG Melgar by placing him in a chokehold.”

In May, NBC News reported that two Marine Raiders were under investigation in the now-concluded Naval Criminal Investigative Service inquiry into Melgar’s strangulation. Last week, the U.S. Naval Institute’s news division reported that the Navy had ordered a one-star admiral, Rear Adm. Charles Rock, to determine if the four would face charges.

“If these allegations of misconduct are substantiated, they represent a violation of the trust and standards required of all service members,” Navy Captain Jason Salata, the director of communications for the U.S. Special Operations Command, told The Daily Beast. “We trust our service members to safeguard our nation’s most sensitive interests and to do so with honor.”

The Daily Beast has learned new details of the grim prelude to Melgar’s death.

There was an ongoing disagreement between the Green Beret and DeDolph over the SEALs’ professionalism, a source familiar with the episode told The Daily Beast. Melgar was upset with lapses in operational security, according to a source familiar with the investigation’s findings. DeDolph and Matthews, both members of SEAL Team Six, were soliciting prostitutes and taking them back to the safe house in Bamako, Mali’s capital city. As The Daily Beast reported last year, Melgar had found the SEALs skimming cash from a fund to recruit informants about local Islamist activity.

“The place ran like a frat house,” the source said.

Melgar was part of a six-man intelligence operation in Mali supporting counterterrorism efforts against al-Qaeda’s local affiliate, known as al-Qaeda in the Islamic Maghreb. Melgar reported the violation to his chain of command, drawing the ire of the SEALs and two Marine Raiders, who were also on the team assigned to assist with counterterrorism.

Then on June 4, 2017, Melgar was invited to an embassy party, and the rest of the team was not. While Melgar was gone, the two SEALs and two Marine Raiders plotted to haze Melgar for the slight, according to the source familiar with the investigation’s findings.

“They planned for hours,” the source familiar with the investigation report said.

DeDolph and Matthews, along with the two Marine Raiders, allegedly confronted Melgar at the safehouse around 5 a.m. DeDolph, a mixed-martial arts fighter, put Melgar in a chokehold. The attackers and Melgar fell onto the bed with Matthews on top of Melgar, according to a source familiar with the inquiry.

DeDolph realized Melgar wasn’t breathing, according to a preliminary investigation report first reported by NBC News. The SEALs tried to resuscitate Melgar with CPR and opened a hole in his throat. They then took Melgar, along with another Fort Bragg-based Green Beret, to a French medical facility, where he was pronounced dead.

At the clinic, DeDolph admitted to an embassy official he choked Melgar, according to NBC News and subsequent reports.

After the SEALs returned to the safehouse, they engaged in a cover-up, according to several witnesses – including cleaning up evidence and coaching witnesses. The charge sheet accuses the members of the conspiracy with “providing a false timeline of events to the Navy chain of command,” and “purposefully” left out the duct tape when making their statements on Melgar’s death. They as well allegedly “disposed of the alcohol” they kept in the shared Army-Navy quarters, and lied to investigators.

A source told The Daily Beast last year that the SEALs filed at least one operational report about the incident and possibly two. At least one of the reports included an account that Melgar was drunk. But Melgar did not drink alcohol, and a toxicology report showed no alcohol in Melgar’s system.

U.S. Special Operations Command’s Salata said the command honored Melgar’s memory and kept Melgar’s loved ones in its thoughts. He pledged unity amongst the U.S.’ elite forces amidst an episode that has sent shockwaves through the special-operations world.

“We will not allow allegations or substantiated incidents of misconduct erode decades of honorable accomplishments by the members of U.S. Special Operations Command. Ours is a culture of professionalism and accountability, which prides itself in being a learning organization that uses critical self-examination in a relentless dedication to improvement,” Salata said.

“The standards expected of special operations are high in every aspect of life. Trust and accountability are the foundational requirements of all service members when conducting our nation’s most complex, sensitive, and high risk operations. We hold ourselves and each other accountable on a daily basis because we know that lives are on the line.”

Logan Melgar’s wife, Michelle, was briefed on the case earlier this month in Norfolk, Virginia, and again this week at Fort Bragg, according to sources. She declined to discuss the case in detail with The Daily Beast, but said she supports the prosecutor and that her goal was to not allow the incident to cause a rift between the Special Forces and SEALs and Marine Raiders.

“While I have faith that the military court will handle this situation in the best possible way, I also understand that the mission continues,” she said. “Our men must work well together, and we need to support them in doing so.”