In scene 2 why is frair in a panic when he finds out that his letter was not delivered to romeo? why is this a key turning point in the plot

If I'm not mistaking, this isn't scene two, however I remember he was panicking because he was afraid Romeo was going to do something stupid (like killing himself or running away) before he found out Juliet wasn't dead. This is a key turning point because if the letter had actually been delivered, Romeo and Juliet could have avoided actually killing themselves.