"I can't breathe." These were the final words uttered by Jamal Khashoggi after he was set upon by a Saudi hit squad at the country's consulate in Istanbul, according to a source briefed on the investigation into the killing of the Washington Post columnist.

The source, who has read a translated transcript of an audio recording of Khashoggi's painful last moments, said it was clear that the killing on October 2 was no botched rendition attempt, but the execution of a premeditated plan to murder the journalist.

During the course of the gruesome scene, the source describes Khashoggi struggling against a group of people determined to kill him.

"I can't breathe," Khashoggi says.

"I can't breathe."

"I can't breathe."