First, let's deal with why your question is important. In the book That Was Then, This is Now, Bryon and Cathy are in a dating relationship. How Bryon treats Cathy, then, is of utmost importance. Cathy's younger brother, M&M, begins using drugs, which seriously concerns Cathy. Bryon eventually turns Mark into the police for selling drugs. Mark is Bryon's foster brother who is taken in by Bryon's parents after Mark is left orphaned. Mark's parents killed each other during a drunken brawl when he was young.
During their younger years, Bryon and Mark have a tight friendship in which they manage to get into trouble and break the law. However, after Cathy and Bryon begin dating, he begins to lose the desire to break laws and get into fights.
Another character, Charlie, is killed saving Bryon and Mark from a fire. Cathy expresses remorse while Mark is unable to feel the same.
I guess I just couldn't see standing there -- alive, talking, thinking, breathing, being -- one second, and dead the next. It really bothered me. Death by violence isn't the same as dying any other way, accident or disease or old age. It just ain't the same.
Bryon becomes closer to Cathy as he matures and begins to part ways with his and Mark's former gang lifestyle. When Cathy expresses concern about M&M's drug use and disappearance, Bryon takes Cathy to look for him for at least a week. When they find Bryon, he is hospitalized for the effects of LSD. Bryon is caring and concerned during this time. However, after turning in his foster brother for selling drugs, Cathy tells him she feels sorry for Mark. Bryon can't take this. Bryon finds he no longer loves Cathy, and they never speak again.