An accurate target

Father took three sons to the wilderness on the prairie. Before arriving at the destination, everything was ready and acted, the father raised a question to the three sons:

"What did you see?"

The boss replied: "I saw the shotgun in our hands, the hare running on the grassland, and the endless grasslands."

Father shook his head and said, "No."

The second child's answer is: "I saw dad, big brother, younger brother, shotgun, hare, and the endless grassland."

The father shook his head and said, "No."

The third child's answer is only one sentence: "I only saw the hare."

Then the father said: "You are right."