Plus the fact that the media themselves had already widely reported that he got shot five times before he even said it himself. The media ran with what the hospital said. It went from being 'struck' five times (which is neutral to how many shots were fired) to 'shot' five times. Given the fact that the doctors were also telling him this, what reason would Pac have to say 'nah, you're wrong, I got shot only once'? Another thing that makes the one shot theory implausible is that the media reported that Fred got hit in the stomach twice. Now I don't know if that's true (in the interview he mentions only one bullet but he said he blacked out after) but if it is, it makes it even more improbable that there was one bullet that caused not only all of Pac's wounds but two wounds in Fred's stomach as well.
Nevermind the fact that the exterior of 2pac's right hand was struck as well and that in the interview at the gun range you can see that he shoots with his right hand. Now if you shoot yourself, how does the bullet strike the hand that's pulling the trigger? It's of course not impossible that he went for the gun with his left hand as he had two guns on him but given the fact that his preferred shooting hand seemed to be his right it's another improbability of the one bullet theory. His exterior right hand being struck would also be in line with what Pac said himself about getting shot as he was reaching for his gun.
Regardless, it's clear that anyone reporting with absolute conviction that he shot himself without putting any of this in context, is showing a clear bias against 2pac's personal integrity despite the fact that nothing he has said about the shooting has been firmly contradicted by any of the evidence or other accounts.