On July 8, an advance team walked the site, the Butler Farm Show grounds, to assess a security threat. Agents worked with local law enforcement and explained what the Secret Service would handle and what law enforcement would be expected to do. Crucially, the Secret Service decided that a group of warehouses to the north of the stage would be excluded from the security zone, despite being only about 450 feet from Mr. Trump’s podium. That was within a rifle’s range
That meant the warehouses were assigned to local law enforcement to secure. The Secret Service and the local police had treated the complex of warehouses just north of the rally site as an observation post. It was considered a place from which to watch Mr. Trump’s crowd — not a place that needed to be watched, itself.
But that created a blind spot, outside the security perimeter but well within rifle range of Mr. Trump. It was exploited by a gunman with no military training and little subtlety, who showed up early and acted oddly enough that police photographed him and distributed his picture, though with no weapon in view...
"When the F.B.I. was able to finally access Mr. Crooks’s cellphones and other electronic devices, agents could see that he had searched for images of Mr. Trump as well as President Biden, Attorney General Merrick B. Garland and even F.B.I. Director Christopher A. Wray.
Mr. Crooks also had at typed in “major depressive disorder” and
searched for dates and places for appearances for both. Biden and Mr. Trump.
When the police reached Mr. Crooks’s body on the roof, he had no identification on him. Officers traced the serial number on his rifle to his father. In his pocket, he carried a remote control to the bombs in his car.
It was not clear if he had tried to use it, or if the bombs were made well enough to explode.
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https://nytimes.com/2024/07/17/us/politics/secret-service-trump-shooting.html