The assassin was locked in an hour in advance, but was "lost"

There is new progress in the Trump assassination case. Wyoming Senator John Barrasso revealed that the Secret Service found the assassin an hour before the incident and identified him as a suspicious person because the assassin carried a rangefinder and a backpack.

However, the Secret Service lost the person.

This makes people think too much, because there are too many "coincidences".

1. The Secret Service controlled all the commanding heights, but missed the roof where the assassin was;

2. The Secret Service found the suspicious person an hour in advance, so why did it lose him;

3. The assassin was found half an hour before the incident. At this time, it should have attracted attention, especially the place where he appeared and the previous suspicious behavior, but he waited until the gun was fired before taking action.

4. How did the assassin know that the building was not fortified? How could he appear in the only shooting position with a rangefinder and a rifle?

Now many people are questioning the US Secret Service. If it is really just negligence, it is not a big deal. But if it is not negligence, the problem is not simple.