St. Leo's is staffed by the Society of the Catholic Apostolate (Immaculate Conception Province), also known as the Pallottines, which is part of the larger organization known as the Union of Catholic Apostolate.

From http://www.sacapostles.org/about-us.html:

Inspired by St. Vincent Pallotti's motto, "The love of Christ impels us," the Society of the Catholic Apostolate (the Pallottines) works throughout the world to further the Catholic Church's mission to renew faith and rekindle charity. As part of the Union of Catholic Apostolate, the Society of the Catholic Apostolate is a group of priests and brothers known as the Pallottines. Pallottine priests and brothers are a group of men who share a life of community, prayer, and apostolic work. They follow the ideas of their founder, St. Vincent Pallotti, who wanted to reawaken faith and love among Catholics. Pallottines work to instill in others a deep conviction of their personal call to live the message of Jesus Christ.

To remain faithful to St. Vincent Pallotti's call to "revive faith and rekindle charity," Pallottine priests and brothers promise the Society consecrated celibacy, poverty, obedience, perseverance, the sharing of resources, and spirit of service. These promises are a sign of the desire to live in a community devoted to service to the people of God. St. Vincent Pallotti saw ministry as having two purposes: to love God and to shower God's love on others.

History of St. Vincent Pallotti

St. Vincent Pallotti was a very modern saint who organized many remarkable pastoral programs that he is considered the forerunner of Catholic action. He was a man of ideas and vision and was able to inspire others to tackle great things. He came from a wealthy family and believed with all of his heart that God meant for the rich to help the poor; the well and able to aid the sick and dying; and for the well-fed to share with the hungry.

St. Vincent Pallotti lived his life for others. He was the founder of the Pallottine Fathers and the Pallottine Missionary Sisters; however, that was but the tip of the iceberg of his accomplishments. He left behind schools, guilds, and institutes that carried the Catholic mission into the very heart of contemporary society.

Born in Rome in 1795, he began studies for the priesthood early. Although he was extremely bright, he was not attracted by studies, though he was ordained a priest at age 23 and earned a doctorate in Theology soon afterward. He was given an assistant professorship at the Sapienza University but resigned soon after to devote himself to pastoral work. Before long, his zeal was known all over Rome. He organized schools for shoemakers, tailors, coachmen, carpenters, and gardeners so that they could better work at their trade, as well as evening classes for young farmers and unskilled workers. He soon became known as a "second St. Philip Neri."

He gave away his books, possessions, and his clothes to the poor, and once dressed up as an old woman to hear the confession of a man who threatened "to kill the first priest who came through the door." In 1835, he founded his two congregations and was instrumental in the founding of a missionary order in England and several colleges for the training of missionaries. He died at the age of 55 and his body lies incorrupt in the church of San Salvatore in Rome. The saint was canonized by Pope John XXIII in 1963.