What is the inciting incident in play Dear Evan Hansen?

Evan Hansen is given a letter of encouragement by his therapist to write himself a letter every day. However, due to a twist of events, this private letter ends up in the hands of Connor Murphy, who is a loner and classmate of Evan's. Connor mistakenly interprets it as a love letter and takes Evan's number down from the letter. Later that day, Connor takes his own life. Evan is called into the Principal's office and learns of Connor's suicide. His parents find the suicide letter signed "Evan Hansen" due to the misunderstanding.