[3][4] Born in Agoo, La Union, he was ordained priest on 6 April 1946 at the young age of 24.

[1][5] During this time, Mabutas became personally acquainted with then-Senator Ferdinand Marcos, who had begun his political career in Laoag.

The two remained on speaking terms throughout their lives, despite Mabutas' later misgivings about the human rights abuses of the Marcos dictatorship.

[1][5] A 1979 pastoral letter Archbishop Mabutas wrote addressing martial law, titled "Reign of Terror in the Countryside", cited human rights abuses and killings of church workers and is notable for having been the first pastoral to be written against Marcos' administration.

[10][1] Some of Archbishop Mabutas' effects have been preserved, and are viewable to the public at the Museo de Iloko in his hometown of Agoo, La Union.