Why is jim casy killed?

The strike is the catalyst for another tragedy for the Joad family. When Tom finds the striking workers, he is reunited with Jim Casy, who has been released from jail and found a new purpose as a labor activist. His lost religious zeal has been transformed into working-class activism, charged by his experiences in jail and traveling to California. Casy is a crusader for the cause; the indecision over his role as a preacher earlier in the novel has been replaced by a fiery conviction concerning the justice of his cause. There is a strong political text to the final scenes with Casy, who compares their cause to that of Lincoln, Washington and the patriots of the French revolution. Steinbeck makes it clear that these activists are facing certain doom, but they will be vindicated eventually. Casy, who sacrificed his freedom for Tom earlier in the novel, makes a final sacrifice in this chapter, the victim of a brutal murder at the hands of the police. Casy has now been a martyr for the Joad family and now for the entire class that the Joads represent.