The USSS is beyond responsible for this, as they are the primary line of defense for Donald Trump. Besides the rooftop, which anyone with common sense would have protected right away, there were many other elevated sites that the agency should've taken care of before that rally. The USSS has all the technology to monitor these threats, from drones to thermal cameras, but they simply chose not to.
While impassioned thoughts and remarks about this situation are understandable, the American people should rest assured that the USSS is already implementing changes with respect to personnel, communications, and technology. The USSS, as well as the Dept. of Homeland Security, is also in dire need of more funding, and while that's no excuse, it's a sound national security proposal that everyone can certainly agree upon.