How does Daniel Silva use imagery in The Mark of the Assassin: A Novel?

Imagery:

"One image remained long after she arrived home, as she lay in bed awake, waiting for Michael. It was the image of Mitchell Elliott and Samuel Braxton, huddled together like a a pair of giggling schoolboys in the darkened garden, toasting each other with champagne."

"The arrowhead struck Astrid in the base of her throat and drove her back, pinning her to the open door. Elizabeth screamed. Astrid's eyes opened wide and her lips parted."