He continued his studies for a master's degree at the Saint Petersburg Roman Catholic Theological Academy where he formed a life-long friendship with fellow cleric Jurgis Matulaitis-Matulevičius.

During the Russian Revolution of 1905, he participated in the Great Seimas of Vilnius and helped draft the program of the Lithuanian Christian Democratic Party.

Būčys was born in the Šilgaliai [lt] village situated on the Šešupė river which acted as a natural border between Lithuania (then part of the Russian Empire) and East Prussia.

[9] Būčys and Andrius Dubinskas [lt] wanted to organize a larger secret cleric society that would include members not only from Sejny but also from Kaunas and Vilnius Priest Seminaries.

They held discussions with clerics in Kaunas and Vilnius, including about replacing Žemaičių ir Lietuvos apžvalga with another publication, but the plans did not come to fruition.

[4] He was also close with Lithuanian professors at the academy: he inherited property of Kazimieras Jaunius and wrote a 2,426-page biography of Justinas Pranaitis though it remains unpublished.

[4] To earn a living, Bučys held masses in Autigny and was chaplain of a girls' agricultural school in Orsonnens [de].

[3] He defended his expanded thesis on Saint Stanislaus, which was translated from Latin to Polish and published in 1902,[11] and earned Doctor of Theology in July 1901.

[6] Upon return to Lithuania in late 1901, Būčys hoped to become an editor of a Lithuanian newspaper and live in Tilsit (present-day Sovetsk, Kaliningrad Oblast).

In his memoirs, Bučys highlighted two weaknesses of his teaching methods – he emphasized ability to think rather than knowledge of facts and spent too much time analyzing anti-religious arguments.

In December 1905, during the Russian Revolution of 1905, Būčys participated in the Great Seimas of Vilnius and became a member of its five-member presidium when Juozas Tumas-Vaižgantas resigned in his favor.

[2] In Saint Petersburg, Bučys contributed articles to Lithuanian (he had his own sections in Šaltinis and Vadovas,[3] Vilniaus žinios, Lietuvių laikraštis, Nedėldienio skaitymas, Draugija, Viltis, Vienybė), Polish (Przegląd Katolicki, Wiadomości Archidiecezjalne, Wiadomości Kościelne, Atenaum Kapłańskie), Belgian (Le Messager du Sacré-Coeur de Jésus), and American (New World in Chicago) press.

They often discussed reviving the Congregation of Marian Fathers of the Immaculate Conception which at the time had only one elderly member, but it had to be done in secret due to various Russification policies.

[4] On 29 August 1909, in a private chapel of auxiliary bishop Kazimierz Ruszkiewicz [pl] at the clergy house of the Holy Cross Church in Warsaw, Matulaitis-Matulevičius became a member of the Marian Fathers and Būčys began his novitiate.

[3] In United States, Bučys served as the pastor of Lithuanian parishes in Sheboygan, Wisconsin (August 1917 – May 1918) and Waukegan, Illinois (June 1918 – July 1921).

[6] At the same time, he edited the struggling Lithuanian daily Draugas (in February–July 1917 and September 1918 – July 1920)[3] and in 1920 established religious weekly Laivas which continued to be published by the Marian Fathers in Chicago until 1990.

[18] He was also a member of the commission that collected a million signatures under a petition to President Warren G. Harding to recognize independent Lithuania.

The idea was supported by Juozas Tumas-Vaižgantas, bishop Juozapas Skvireckas, and others and the construction of the Christ's Resurrection Church started in 1934.

He represented Lithuania and was elected as honorary member to the committees at the international Eucharistic congresses in Sydney, Australia (1928), Carthage, Tunisia (1930), and Dublin, Ireland (1932).

It was supported and encouraged by the Vatican in hopes that respecting and leaving the traditional Byzantine customs would allow implementing Catholic dogma and teaching among Eastern Orthodoxs.

[24] Bishop Pranciškus Karevičius [lt] (also a member of the Marian Fathers), papal internuncio Riccardo Bartoloni, and Prime Minister Augustinas Voldemaras agreed on the mission in Lithuania and the use of the St. Michael the Archangel Church for its purposes.

[3] He visited Russian communities in eight countries (including France, Belgium, Yugoslavia) in 1930 and Marian Fathers in United States in 1931.

He had a round-trip ticket and was expecting to return to United States, but received orders from the Vatican to remain in Lithuania and work among local Russians.

[24] In October 1934, he held Eastern rite masses at the Church of St. Francis Xavier that attracted attention from Orthodox intelligentsia who were dissatisfied with the services of Metropolitan Eleutherius [ru].

The pope refused and appointed Bučys as the head of the new papal Mission for Spiritual Assistance for the Russians of Lithuania established by the Congregation for the Oriental Churches.

After the death of Pope Pius XI in February 1939, Bučys was reelected as the Superior-General of the Marian Fathers in July 1939 and finally allowed to leave for Rome.

[6] He suffered a brain hemorrhage in September 1951 and a day before his death received permission to hold Latin rite masses.

[3] His popular works include books about the Lourdes apparitions (first published in 1909, third edition in 1943), cautionary tales promoting the temperance movement (in 1925 and 1939), parents' right and obligation to raise and educate their children (in 1927), a conversation about the soul (in 1930).

[3] He left other thick volumes of manuscripts on his thoughts for the Marian Fathers, on good behavior, and miracles of Jesus as well as an extensive biography of Justinas Pranaitis.

[2] He had a good memory and knew more than ten languages (he could write rather fluently in six of them – Lithuanian, Latin, Polish, Russian, French, and English).