People had been shocked by Brady's photograph because it showed the real state of dead bodies in the war.
We can arrive at this answer because:
Brady was a very influential photographer after the American Civil War.
That's because he released a photograph, which shocked the country, but was very important to show how violent and devastating the war was.
That's because Brady photographed dead soldiers in a field.
This was one of the first times that corpses were shown so clearly in photographs distributed across the country.
Brady's photograph showed the bodies swollen, decomposing, abandoned in the field and with their pockets rummaged, which showed that someone had gone through them for something of value.
