On April 12, 1975, United States Ambassador to Cambodia John Gunther Dean offered high officials of the Khmer Republic political asylum in the United States, but Sirik Matak, Long Boret and Lon Non, along with other members of Lon Nol's cabinet, declined – despite the names of Boret and Sirik Matak being published by the Khmer Rouge in a list of "Seven Traitors" marked for execution. 

This is Sirik Matak's written response to the ambassador:

Dear Excellency and friend,

I thank you very sincerely for your letter and for your offer to transport me towards freedom. I cannot, alas, leave in such a cowardly fashion.

As for you and in particular for your great country, I never believed for a moment that you would have this sentiment of abandoning a people which has chosen liberty. You have refused us your protection and we can do nothing about it. You leave us and it is my wish that you and your country will find happiness under the sky.

But mark it well that, if I shall die here on the spot and in my country that I love, it is too bad because we are all born and must die one day. I have only committed the mistake of believing in you, the Americans.

Please accept, Excellency, my dear friend, my faithful and friendly sentiments.

Prince Sirik Matak

Shortly after the surrender to the Khmer Rouge was announced, Sirik Matak sought refuge at the Hotel Le Phnom, where the International Red Cross was attempting to create a safe zone. He was turned away once the Red Cross learned that his name was on the list of “Seven Traitors”. Outside the hotel, Sirik Matak talked to reporters and distributed copies of his letter to Ambassador Dean. François Bizot reported that Sirik Matak then sought asylum at the French Embassy and that the Khmer Rouge threatened to come into the compound and remove certain individuals by force if they did not go voluntarily. Accompanied by the French Vice-Consul Jean Dyrac and journalist Jon Swain, Bizot took responsibility for informing Sirik Matak of the Khmer Rouge's demands, at which point he voluntarily surrendered and left on a Khmer Rouge Jeep with Mam Nai. Sirik Matak and the officials that remained along with him were executed by the Khmer Rouge on April 21, 1975.