He served in South Texas from 1853 to 1872, traveling long distances on horseback to minister to Catholics living on isolated ranches along the Rio Grande.

After deciding to join the Missionary Oblates of Mary Immaculate, he began his novitiate at Notre-Dame-de-l'Osier in 1851, and spent several months at the Marseilles major seminary.

[4] In 1856, the priest originally in charge of building the Immaculate Conception Cathedral in Brownsville, Father Verdet, was returning from a trip to France when he was drowned in a shipwreck off the Louisiana coast.

[1] He designed Our Lady of Visitation Church in Santa Maria, another Gothic Revival edifice, and St. Joseph's chapel at the Toluca Ranch in Progreso.

At least three times a year he covered a large territory spanning 70-120 ranches, where he would preach, catechize young people, hear confessions, and perform wedding and funeral rites.

A neighbor once saw him carrying lumber and tools into a shack on the outskirts of town; on investigation, it turned out that Kéralum was building a coffin for the impoverished woman who had died there.

In 1882 some cowhands found his remains in the brush, identifiable by his belongings: a rosary fragment, a chalice and other ceremonial items, and an old saddle hanging from a tree limb.

A life-size crucifixion scene, erected in 1920, marks the spot in Mercedes where his remains were originally interred before being transferred to San Antonio, Texas.

Roy Snipes of Our Lady of Guadalupe Catholic Church in Mission, Texas, presented the visitors with a recording of a corrido, or Mexican folk ballad, written in Kéralum's honor.

A member of the Fernandez family from Toluca Ranch wrote a history which Snipes adapted into a play about Kéralum, which is performed once a year at La Lomita Chapel.