How does John Hart use imagery in The Last Child?

Imagery:

"Johnny saw a shower of sparks, the top of a car and a motorcycle that cartwheeled once before the body came over the rail. One of the legs bent impossibly, the arms churned and Johnny knew it was a mistake, a pinwheel that screamed with a man's voice. It landed at Johnny's feet with a wet thump and the double snap of breaking bones. His eyes were open and they were the most amazing blue."