Transcript of an audio recording from Jamal Khashoggi's brutal death reportedly describes him gasping for air in his final moments.

A source, who was briefed on the investigation and read a translated transcript of the recording from the October 2 killing, told CNN that the audio suggested a carefully planned execution and not a botched interrogation as previously touted by the Saudis.

The transcript also describes "sawing" and "cutting" that could be heard along with screaming.

Men in the room were reportedly told to "put earphones in" or "listen to music" to block out the gruesome noises.

The transcript of an audio recording from Jamal Khashoggi's brutal killing reportedly describes the Saudi journalist gasping for air in his final moments.

A source, who was briefed on the investigation and read a translated transcript of the recording from the October 2 killing, told CNN that the audio suggested a carefully planned execution and not a botched interrogation as previously touted by the Saudis.

Descriptions of the tape recounting how Khashoggi suffocated have previously been reported. But CNN's report on Sunday is the fullest account of the transcript in Western media to date.

According to the source, the transcript began with Khashoggi entering the Saudi Consulate in Istanbul at about 1:15 p.m. to pick up routine paperwork for his coming marriage to his fiancée, Hatice Cengiz, who was waiting outside for him.

Khashoggi quickly realized something about the situation was off, as he recognized a man waiting inside, identified by CNN's source as Maher Abdulaziz Mutreb, a former colleague and a prominent aide to Crown Prince Mohammed bin Salman.

Read more: US hits 17 Saudis with sanctions over Khashoggi, including crown prince's top henchman who reportedly directed killing via Skype

According to the source, Khashoggi asked the man what he was doing there.

"You are coming back," Mutreb told Khashoggi.

"You can't do that," Khashoggi responded. "People are waiting outside."

Mutreb was also named by Turkish officials as one of the 15 Saudis suspected to have acted in Khashoggi's killing.

At that point the dialogue ended, the source said, as several people closed in on Khashoggi, who was left gasping for air in his final moments.

"I can't breathe," Khashoggi repeated several times. The transcript reportedly described screaming and gasps.

Other men, including a voice identified by Turkish authorities as Dr. Salah Muhammad al-Tubaiqi, the head of forensic medicine at Saudi Arabia's Interior Ministry, could be heard along with Khashoggi's muffled pleas, the source said. The transcript then described "sawing" and "cutting" sounds.

Al-Tubaiqi could reportedly be heard telling the team in the room to block out the noise.

"Put your earphones in or listen to music like me," he said, reportedly according to the transcript.

Notably, the transcript describes at least three phone calls placed by Mutreb to someone who, according to previous assessments of the recording, is widely thought to be a senior Saudi official, possibly Crown Prince Mohammed bin Salman's closest adviser, Saud al-Qahtani, or possibly even the crown prince. Mutreb reportedly gave the undisclosed person on the other end of the line step-by-step details of what transpired: "Tell yours, the thing is done, it's done."

Links to the crown prince

Saudi Crown Prince Mohammed bin Salman. (Photo by Leon Neal/Getty Images)

Calls for sanctions have grown louder in recent weeks, as details from the investigation into Khashoggi's killing continue to close in on the Saudi leadership.

Last week, senators from across party lines announced with a "high level of confidence" that Crown Prince Mohammed was "complicit" in Khashoggi's killing and introduced a measure calling for the crown prince to be "held accountable" for numerous human-rights abuses.

The move, led by Republican Sens. Marco Rubio of Florida, Lindsey Graham of South Carolina, and Todd Young of Indiana and Democratic Sens. Dianne Feinstein of California, Ed Markey of Massachusetts, and Chris Coons of Delaware, pins the blame directly onto the crown prince and hopes to spur the government and the international community to punish him accordingly.

Read more: Senators are now confident that Crown Prince Mohammed bin Salman was 'complicit' in Jamal Khashoggi's death

"There is no doubt that Crown Prince Mohammed bin Salman knew about the murder of Saudi journalist Jamal Khashoggi, condoned it, and at worst was actually involved in directing it," Rubio said in a statement Wednesday.

President Donald Trump and, separately, a small group of senators were briefed by the CIA on the investigation into Khashoggi's death. The CIA has previously concluded that the crown prince ordered Khashoggi's killing based on several pieces of intelligence, including the audio recording and security footage.

But the resolution is set to face hurdles by the Trump administration, as the president has recently doubled down on his defense of the Saudi crown prince and said the US-Saudi relationship is "paramount" in his decision making.