Note to Romeo and Juliet, 3.2.121: "But with a rearward following Tybalt's death, / 'Romeo is banished'?"

Romeo and Juliet,
Act 3, Scene 2, line 121.
This is the conclusion of a question which begins at line 116. The whole question may be condensed as follows: if woe loves company, why wasn't the news of Tybalt's death followed only by the news of the death of my mother or father, which would have been bad enough, without the overwhelming ambush of the news that Romeo is banished? [A "rearward" is an ambush meant to stop an advancing army from pursuing a retreating army.]