They were intentional shots. If you look at the hotel on Google earth you can see that his two shooting locations in the suites were one covering the concert venue and the other one directly aimed at the fuel tanks.
With the sheriff hinting at accomplice possibility, I am wondering if a second person was supposed to move the car over by the tanks and detonate it and chickened out or something, thus forcing Paddock to try and take some pot shots at the tanks.
Two holes in two big white tanks. Pretty bad aim.