Conversation so far:
when did Yagan die?
When the party of settlers arrived, they found Yagan dead and Heegan dying.
what year was this?
1833.
how did he die?
William Keates shot Yagan, and James shot Heegan, another native, in the act of throwing his spear.

Question: why was he killed?
Self-contained rewrite: Why was Yagan killed?