Conversation so far:
What was his Thích Quảng Đức's religious background?
Thích Quảng Đức's religious background was Mahayana Buddhism.
Was most Thích Quảng Đức's country also buddhist?
The religious composition of Vietnam at the time estimated the Buddhist majority to be between 70 and 90 percent.
If the Vietnamese buddhists were the majority, then why were they being persecuted?
President Diệm was a member of the Catholic minority, and pursued discriminatory policies favoring Catholics.
How did the people react to President Diệm pursuing discriminatory policies favoring Catholics?
Many switched to Catholicism to help their own careers, and the remaining Buddhists were discontent.
So did Catholics then become the majority in Vietnam?
Is there anything else interesting about Thích Quảng Đức besides his religion?
Buddhist discontent erupted following a ban in early May on flying the Buddhist flag in Huế on Vesak, the birthday of Gautama Buddha.
Did the Buddhists protest or do anything to fight the ban?
A large crowd of Buddhists protested the ban, defying the government by flying Buddhist flags on the Buddhist holy day of Vesak and marching on the government broadcasting station.
What happened to the Buddhists when they protested?
Government forces fired into the crowd of protesters, killing nine people.

Question: What was the reaction to those killings?
Self-contained rewrite: What was the reaction to the killings of the Buddhist protestorsz?