Complex sentence: Willis E. Hartshorn, director of the International Center of Photography, asserted the photograph's veracity, suggesting that the militiaman had been killed by a sniper firing from a distance while posing for a staged photograph.
Split into simpler sentences: Willis E. Hartshorn, director of the International Center of Photography, argued against the claims that the photograph was staged. He suggested that the soldier in the photograph had been killed by a sniper firing from a distance while posing for the staged photograph.