The young Jose R. Calderon was his school's most outstanding student from first grade to fourth year high school. He showed interest in the arts, particularly in drama and dance, and was active in the Methodist Youth Fellowship.
Addressing his classmates as their valedictorian upon their graduation from high school, he stressed the role of the youth in helping create a society where economic justice and political freedom prevail: "We may not live to see the fulfillment of this dream but certainly, we can lay down the foundation of its beginning. Let us therefore dedicate our golden hours, enthusiasm and energy to the challenge of the times – economic development, freedom and security."
When he entered the University of the Philippines as a political science major, campus activism quickly drew him in. He joined the Nationalist Corps of the UP Student Council, the Samahang Demokratiko ng Kabataan and the Alpha Sigma fraternity. Summer breaks found him and his friends living in the rural areas, as part of a "learning from the people" campaign.
Calderon was active in the big demonstrations in Manila, in what would later be known as the First Quarter Storm of 1970. When student rallies were violently dispersed on January 30 and 31 in Mendiola, near Malacanang Palace, he was there.
Reared in the Methodist Church, Calderon interpreted his growing involvement in activism not only as a social demand but as an expression of his Protestant faith. When in July 1971 he finally decided to leave the university and commit himself fulltime to the movement, he wrote his parents:
"Kung tatandaan lamang ninyo na narito sa kilusan ang aking kaligayahan at wala sa pag-aaral, marahil ay matutuwa pa kayo sapagkat ang anak ninyo ay nakatagpo ng magandang kahulugan para sa kanyang buhay—isang buhay na sa aking palagay ay higit na kristiyano at maka-Diyos kaysa sa palaging pagpunta sa kapilya nang hindi naman isinasabuhay ang turo ng bibliya." (If you consider that it is being in the movement and not being a student that makes me happy, you may be glad that your son has found positive meaning in life – it’s a life that I think is more christian and godly than if one were to spend his time praying in the chapel but without practising what the Bible teaches.)
He asked his parents not to blame themselves for his decision. "Blame the system," he said, "which created millions of poor people, exploited by foreigners and a few greedy Filipinos." As long as that kind of system prevailed and a fairer system not put in its place, he wrote, "more parents will lose their children, more children will lose their parents, and more husbands or wives will lose their spouses." He was ready, he declared, to give up his life in the struggle to establish this radical change in society.
In July 1971, Calderon went to the jungles of Isabela in Northern Luzon to join the New People’s Army (NPA), then a newly-organized guerrilla group. In his letters, he described the numerous hardships and sacrifices they were going through, as the Marcos regime launched all-out efforts to eliminate them while it was still early enough. Taking the name Ka Elmo, he served with the NPA until he was killed in a battle with government forces in May 1974 in San Mariano, Isabela.
His letters have been compiled by his family in a book Mga Liham ni Ka Elmo (Letters from Ka Elmo), a record of his patriotism and bravery, his efforts to overcome material and emotional difficulties, and his unwavering solidarity with the people.