Thich Quang Duc had prepared himself for his self-immolation through several weeks of meditation and had explained his motivation in letters to members of his Buddhist community as well as to the government of South Vietnam in the weeks prior to his self-immolation. In these letters he described his desire to bring attention to the repressive policies of the Catholic Diem regime that controlled the South Vietnamese government at the time. Prior to the self-immolation, the South Vietnamese Buddhists had made the following requests to the Diem regime, asking it to:

1. Lift its ban on flying the traditional Buddhist flag;

2. Grant Buddhism the same rights as Catholicism;

3. Stop detaining Buddhists;

4. Give Buddhist monks and nuns the right to practice and spread their religion; and

5. Pay fair compensations to the victim’s families and punish those responsible for their deaths.

When these requests were not addressed by the Deim regime, Thich Quang Duc carried out his self-immolation.  Following his death,  Thich Quang Duc was cremated and legend has it that his heart would not burn.  As a result, his heart is considered Holy and is in the custody of the Reserve Bank of Vietnam.

Bhuddistinformation.com

Quảng Đức’s last words before his self-immolation were documented in a letter he had left:

«Before closing my eyes and moving towards the vision of the Buddha, I respectfully plead to President Ngô Đình Diệm to take a mind of compassion towards the people of the nation and implement religious equality to maintain the strength of the homeland eternally. I call the venerables, reverends, members of the sangha and the lay Buddhists to organize in solidarity to make sacrifices to protect Buddhism.»^[5]

Wikipedia