Former Las Vegas Metropolitan Police Department officer Chris Carroll made the claim 18 years after the attack in the city.
Shakur was travelling in a car along the Strip when another vehicle pulled up and a gunman inside opened fire, shooting him several times.
Mr Carroll said Shakur’s swearing was in response to the officer’s question “Who shot you?” Shakur then lost consciousness, was taken to hospital where he was put on a life-support machine and then died six days later at the age of 25. But his murder remains unsolved.
Carroll was on the city’s bike patrol squad and was reportedly the first officer on the scene on September 7, 1996. He said as he opened the car door, a blood-covered Shakur “fell into him” and he pulled him out of the vehicle.
He recalled to Vegas Seven: “I immediately notice that the guy’s got a ton of gold on-a necklace and other jewellery – and all of the gold is covered in blood. That has always left an image in my mind.”
The officer claimed he had asked the rapper who shot him several times, but Tupac would not answer.
Carroll said: “I kept asking over and over, ‘Who did this? Who shot you?’ And he basically kept ignoring me. And then I saw in his face, in his movements, all of a sudden in the snap of a finger, he changed. And he went from struggling to speak, being noncooperative, to an ‘I’m at peace’ type of thing. Just like that.”
He added: “He went from fighting to ‘I can’t do it.’ And when he made that transition, he looked at me, and he’s looking right in my eyes. And that’s when I looked at him and said one more time, ‘Who shot you?’
“He looked at me and he took a breath to get the words out, and he opened his mouth, and I thought I was actually going to get some cooperation. And then the words came out: ‘**** you.’
“After that, he started gurgling and slipping out of consciousness. At that point, an ambulance showed up, and he went into unconsciousness.”
Shakur was a front passenger in Death Row Records founder Suge Knight’s BMW when several occupants pulled up in a white Cadillac and one opened fire at an intersection.
