When he was back in the Philippines in 1918, he attended Regency at Vigan Seminary. Soon he was in the United States, where, this time, he took up theological studies at Woodstock College, Baltimore, Maryland. At length he was ordained as priest in Georgetown, Washington, D.C., in June 1925 and proceeded to spend his Tertianship at St. Andrew-on-Hudson, Poughkeepsie, New York.
Returning as priest to the home country in 1927, he was initially assigned to the College of St. Joseph as professor. After spending some three years there as an academic, he was finally assigned as missionary to various places in Mindanao. These places included Dipolog in Zamboanga, Cagayan in Misamis Oriental, Butuan and Cabadbaran in Agusan, Jolo in Sulu, Plaridel in Misamis Occidental, Gingoog in Misamis Oriental, Iligan and Dansalan (Marawi) in Lanao.
When the war broke out in 1941, Father Agustin was in Iligan, where he quickly found ways to work with the guerrillas operating in the place. He secretly provided them with food, clothing, medicines and information about the whereabouts of Japanese patrols, all for which he was later to be called by the Japanese as a “very bad, very bad person.”
At the same time, Father Agustin was ministering to the spiritual needs of his flock, and he deemed it his duty to include those who had fled in the mountains.
Such activities could not long evade the suspicious eyes of the Japanese authorities. And so he was frequently picked up for questioning and detained intermittently for small periods of time. But he was still relatively free.
Being known as one trusted by the local people, he was also blamed for aiding in the disappearances—which the Japanese referred to as “escapes”—of some select personalities from the place. By this time, Father Agustin knew that the Japanese authorities were getting fed up with him.
Father Agustin was eventually taken into custody. It turned out to be a long, difficult and final custody. He was brought to Cagayan de Oro, where he was tortured for giving aid to the guerrillas.
Emaciated and physically broken, he was, after a while, brought under guard to Manila and imprisoned at Fort Santiago in a cell which he shared with many other Filipino and American prisoners. In that cell, the prisoners could only squat all day; no talking was allowed, and so when Father Agustin offered words of comfort to those who needed them, he was punished with more torture.
Death came to Father Agustin on October 12, 1943. After having been handed down a guilty sentence by a Japanese military court, he was shot, along with some other prisoners, the following day. He refused to turn his back on the firing squad. Instead he knelt down to pray, which made his would-be executioners hesitate, as they did not want to kill him in that position of supplication to the Almighty. When the volley rang out, he fell into the grave he himself was earlier made to dig.
Link (here) to the original full piece written by Ma. Merceditas N. Gutierrez, Father Agustin's great gand niece.