And Robert Capa, how was he to know?
As the ramps were lowered and the air turned lead
and the marines before him dropped into the water,
that those photographs he took -
Sheers begins as if in the middle of a sentence while telling a story. This technique is known as  in media res , Latin for ‘in the middle of things’. The effect is a hook that draws the reader into the narrative. 
 The question ‘how was he to know?’ is  rhetorical , creating a feeling of rapport between the speaker and the listeners.
Happy Accidents