Seems to me that if you repeatedly allow events in venues such as this one which placed 22,000 people beneath a perfect sniper position and well within effective range of the weapons used that sooner or later somebody will seize the opportunity.
This could have been prevented with better security. Remember, Las Vegas has been specifically targeted by ISIS, and given their record it appears it would have been quite appropriate to devote some serious attention to threats against large gatherings. It is apparent to me that Las Vegas did not do this. One hotelier did take steps, Steve Wynn, and he says the guy could not have pulled it off from his hotel.
The security they had didn’t consider the basic security situation: a gathering of 20+ thousand people below a perfect sniper(s) position. Without guard towers manned with sharpshooters watching the building you have what is basically a huge attraction (much like so called “gun free” zones) for anyone wanting to harm people. LA PD revealed in the last few days that they have been doing this for years at large gatherings such as the Academy Awards.
An even better alternative would have been to have held the concert at a different, less vulnerable location.
Seems to me that the families of the dead and those who were wounded have good cause to sue for negligence on the part of the event operator. (I also believe that is true of every other “gun free” zone where similar murders have occurred).
Allowing guns in this gun-free zone would not have changed the outcome.