Depends on the drone.Seems like a drone would have picked up on the shooter.
I reckon there weren't any available.
Typically, drones have relatively short battery life. You’d need one fairly large with a good camera, and a large screen from viewing.
For the size of the area, Mark 1 eyeball is probably sufficient and cheaper to operate.
I’m not saying he couldn’t have been seen with a drone. Just that drones aren’t the greatest thing ever for every situation. Maybe they should be incorporated in to SS security. Would at least provide some footage for the investigation afterwards.