What is The Death of Skip's Mother?

Skip's mother lives in the United States and he doesn't realize she's having health issues. He is in the U.S. for more than a year and doesn't go visit her during that time. He learns of her death just as he's beginning to work with Trung, who is a double agent. Skip feels remorse at having left his mother, who was a widow with only one child, but he also feels a sense of relief. Her death represents his freedom because he feels he no longer is responsible for her happiness.