Conversation so far:
When did Patrice Lumumba's deposition of Kasa-Vabu happen?
5 September 1960, Kasa-Vubu announced the dismissal of Lumumba. Patrice Lumumba heard of the firing and made three broadcasts, defending his government and declaring Kasa-Vubu to be deposed
What was the joint session in which Patrice Lumumba was in about?
The Parliament held a joint session between the Chamber of Deputies and the Senate. Though several members short of a quorum, they voted to grant Patrice Lumumba emergency powers.

Question: Why did they give him emergency powers ?
Self-contained rewrite: Why did the Congolese Parliament give Patrice Lumumba emergency powers ?