The dude was shooting for 9 min. The hypothetical cop would have been better off taking the 2.5 min to jog 1/4 mile to the hotel, and then the 1 min to ride the elevator up, and then shooting him from inside the room, rather than take long shots.
I'm going to go out on a limb and say that a vast majority of LEO's with AR's in their trunks don't know a .223's 500m ballistics, don't have BDC optics, and if they have A2 iron sights, don't know what that little wheel in the carrying handle is for.
Not to mention the difference between qualifying at 100m and in on a carbine, and going for a semi precision shot. Not exactly the same trigger/breath control there. That's the amateur hour analysis.
Assuming you got the 1 of the handful of cops in Vegas they knew all that, they'd know they didn't have the dope handy for the extra elevation holdover, they had no way of estimating the winds at 32 floors up and between skyscrapers, at night and they would be better off counting floors up and windows in and radioing the guys position to the folks that were closing in.
Returning fire from street level is a fools game unless we got lucky and one of the precision marksman, AND his rifle were at the concert.
Freak, I don't know if you are being internet hard, or really think that, but no LEO agency, and hopefully no individual cops are going to actually say "*expletive deleted*ck those innocents, I guess it's collateral damage." before they start shooting.