Conversation so far:
When did the deposition happen ?
On 13 September, the Parliament held a joint session between the Senate and the Assembly.
What was the joint session about ?
Though several members short of a quorum, they voted to grant Lumumba emergency powers.

Question: Why did gave him emergency powers ?
Self-contained rewrite: Why did the 13 September joint session of Parliament Senate and Assembly give Patrice Lumumba emergency powers?