Which sentences in this excerpt from F. Scott Fitzgerald's "Winter Dreams" reflect Dexter's heartlessness?

The sentences that reflect Dexter's heartlessness in this excerpt from F. Scott Fitzgerald's Winter Dreams are:

"It was strange that neither it was over nor a long time afterward did he regret that night."

"Nor id it matter that by his yielding he subjected himself to a deeper agony in the end and gave serious hurt to Irene Scheerer, and to Irene's parents, who had befriended him. Dexter Green is the son of a grocery store in a small town called Black Bear in Minnesota, USA.