Second, there were helicopters buzzing the "Strip" taking background radiation readings.
Third, I also saw some mysterious black trucks with no markings, police blue lights, and satellite dishes on top of them. I did not get a picture myself, but they looked like this:
Some Internet searching uncovered that they are a National Guard unit called the "Civil Support Team," one of 57 such teams in the US. They are a National Guard unit that specializes in responding to incidents involving Weapons of Mass Destruction. These are referred to as CBRN (Chemical, Biological, Radiological, Nuclear) weapons.
Ever since the shooting on October 1, 2018, they have begin to take security more seriously.
More on my Vegas trip in another post...