Final answer:
Cassie reacts to the news with shock and grief.
Step-by-step explanation:
In the given passage, Cassie's reaction to the news that her father told about T.J. is shock and grief.
She is devastated to learn that her father had T.J. and his family murdered before they left.
This revelation leaves her broken and overcome with emotions, as depicted by her paroxysm of grief and her nodding when asked if her father had them murdered.