The extra sets of eyes will help to some degree, but it still doesn't change the odds more than a tiny bit. You'd need a cutting-edge defensive tool - something like a counter-sniper Lidar unit - to pinpoint a shooter's location quickly (they're already using the acoustic type gunshot locaters at events such as the Boston Marathon, but those are mostly effective inside 200 yards or so).
Without high-tech gadgets to speed up the response, future incidents such as Travis describes could be as bloody as Las Vegas, or worse.
The original info I had gotten was from Sean Hannity via an interview of Bill O’Reilly days after the Las Vegas shooting.