There are three reviews underway into the SEAL Team Six raid in Yemen last month that killed William "Ryan" Owens and some civilians, the Pentagon said today.

Owens was killed during a Jan. 29 nighttime raid targeting a rural compound in southern Yemen believed to be a key planning location for al-Qaeda in the Arabian Peninsula (AQAP). The mission was designed as an intelligence-gathering mission on the terror group, but Owens' death led Sen. John McCain, R-Arizona, to question the White House spokesman’s assessment that the mission had successfully completed its objectives and was “a huge success.”

Over the weekend Owens' father, William Owens, told the Miami Herald that he wanted an investigation into the Trump administration's decision-making that signed off on the raid.

"I want an investigation," he told the newspaper. "The government owes my son an investigation."

The family declined further comment when contacted by ABC News on Monday.

"There already are multiple investigations going on about this," Capt. Jeff Davis, a Pentagon spokesman, told reporters today, including something known as a "15-6" investigation.

In addition, "there’s an aircraft mishap investigation being done by the chain of command, there’s a civilian casualty assessment being done from [U.S. Central Command]. These are all still in progress," Davis said.

Here is a look at what those terms mean.

The investigations

U.S. Central Command (Centcom) confirmed that a 15-6 investigation is underway into the circumstances of Owens' death that is being conducted by the Navy.

A 15-6 investigation refers to Army regulation 15-6 that allows commands to appoint investigating officers to conduct informal investigations of a military incident or military fatality.

The deaths of all American service members deployed overseas lead to investigations conducted by investigating officers selected from the chain of command.

Family members are provided with copies of the final investigation reports, but they are only releasable to the general public through Freedom of Information Act (FOIA) requests.

A separate review is under way to determine the procedures and circumstances that led to the destruction of a Marine MV-22 Osprey called in to medevac SEALS wounded in the intense firefight.

The Osprey became inoperable after the crew made a "hard landing" that injured crew-members and disabled the aircraft, according to military officials. It was later destroyed by a U.S. airstrike to prevent it from going into the hands of AQAP fighters. Davis said the mishap investigation is also being conducted by the chain of command, presumably a reference to Centcom.

Centcom has also been conducting a civilian casualty credibility assessment that is triggered when allegations of civilian casualties are made, according to military officials.

Centcom launched that assessment shortly after the raid and determined there were some civilian casualties and is still looking to see if there are more casualties. But as Davis said today, officials are still in the assessment phase and if the allegations are found credible, then Centcom will launch an actual investigation into civilian casualties.

“We’re still in the first step. We’re in a credibility assessment," Davis said.

A defense official later said it was better to characterize the three reviews as a casualty investigation and separate assessments into civilian casualties and the aviation mishap.