Police admit high-rise gun massacre is 'nightmare security scenario' as more events prepare to open

New York City Police Commissioner James O'Neill said: "We do understand that no city or town in this country is completely immune to such unbridled hatred."

The Las Vegas gunman's perch in a 32nd-floor hotel room overlooking 22,000 people jammed into a music festival below is the kind of nightmare scenario police dread in places where big crowds and high-rises mix.

From two broken windows at the Mandalay Bay Resort, Stephen Craig Paddock had an unobstructed view to rain rapid-fire bullets on the crowd, with few places for people to hide.