On Saturday, shots were fired during Trump's campaign rally in Butler, Pennsylvania. The former president sustained a gun wound to his right ear and was briefly hospitalized. The gunman killed an audience member and wounded two others in the crowd before being neutralized by the Secret Service.
"Someone should have been on the roof or securing the building so no one could get on the roof," a former senior Secret Service agent familiar with the planning told the broadcaster.
If an officer had been on the building, the gunman likely "wouldn't even attempt what he attempted," Anthony Cangelosi, a former Secret Service agent with experience in protecting presidential candidates, said.