I mean, the simple “We don’t know whats going on, get Trump off the stage...” Like, that’s the least that could have been done.
The intital sightings of this guy were well before Trump went on stage.
They could easily just delayed the start until they sorted things out. Using a range finder is kind of ominous.
Even more simple, take him and his backpack into custody. No one needs a rangefinder to just watch a rally.