They wouldn’t want to put a Secret Service agent on a sloped roof.

Viva Frei - "They wouldn’t want to put a Secret Service agent on a sloped roof. Because that would be a security concern. So they secured it from the inside. Which means that Secret Service was in the building from which a sniper was shooting the President from the unsecured sloped roof."

https://x.com/i/status/1813416240255291607