Who is Chaz?

Chaz, in Paul Fleischman's Whirligig is one of the most popular people at Montford, the private school our main character attends. Chaz is known for throwing large elaborate parties, and this night is no exception. Chaz has planned a black and white themed party completed by a life-sized chess board painted on his tennis court.
Chaz’s party becomes the catalyst for Brent’s bad choices. Brent is worried that he wasn’t invited to the party despite Jonathan’s promises that it will be okay: "

Trust me! I'm his friend. You're my friend. Therefore, you and Chaz are friends. As was proven by theorem 50 in chapter 6. Stop worrying! It's party time!

Once the boys arrive, Jonathan remembers that they were supposed to dress in black and white; Brent instantly is upset and feels left out. His first interaction with Chaz is embarrassing as Chaz decides his last name, Bishop, means he's a human chess piece and mimics pushing him around the room.
Brent thinks to himself that he

felt like slugging Chaz, but knew his tormentor was taller, more muscled, and the de facto ruler of their class besides. If Chaz said that easy listening music was hip, then it was. Losing his cool here would be suicide.

Uncomfortable at the party, he decides to drink to calm down and fit in. The scotch and soda give him the courage to talk to Brianna. However, she rebukes him, in front of the entire party:

You're like a leech or something! Get off of me! Can't you take a hint? Go bother someone else! And that goes for at school too!" devastating him and making him want to die of embarrassment.

Chaz, the jovial host, uses the awkward moment to tease Brent, only making the moment even worse, yelling out that he has no manners and trying to send him to a time out:

"Bishop to penalty bench," he called loudly. "Ten minutes, for sexual harassment."

Brent, now intoxicated, chooses to drive home and listens to the voice in his head that tell him "You have the power to end your life. Now." He closed his eyes, deciding to commit suicide.
However, the result of this action was not his death, but the death of a young girl, Lea Zamora. The action sets the novel on its course, as Brent begins to travel the country learning about himself and performing restitution for the results of his choices.