A few Campos theories:
1). Campos is an even bigger hero having caught Paddock off guard before his attack. Paddock was actually planning an even bigger attack with explosives in his car, Campos surprised him, he resorted to shooting at the concert from the windows after firing at Campos.... Campos's arrival also prevented accomplices from participating which explains the number of weapons. Doesn't explain the questions surrounding Campos and what he was doing between being shot and the cops arrival, why he didn't call for backup, why he is still a ghost. Why cops reported the timeline the first timeline they did.
2). Campos is an accomplice. Doesn't explain how he got shot or why 200 rounds went through the hallway. Campos was an accomplice and he was in the hall setting up cameras or something, but Paddock decided Campos was a liability (or maybe they had some disagreement?) and decides to turn on his partner, and fires at Campos when he isn't expecting it and is down at the other end of the hall setting up cameras and securing doors. Somehow Campos survives the fire... isn't sure what to do... this is why he doesn't call for backup on his radio or call 911. When cops arrive he invents the story that was the first timeline reported by authorities.
3). Campos was in shock after being shot at and disoriented, high on adrenaline, heat of the moment whatever... so he didn't accurately recall the events and hesitated to call for backup...