Eugene Bossilkov was born in 1900. He was ordained a priest on 26 July 1926. He was sent to Italy, to the Pontifical Oriental Institute in Rome, to specialise in Eastern Church studies. He defended his doctoral thesis there. In 1934, he was appointed a parish priest in the village of Bardarski Geran.
He stood out as a great preacher. In the wake of World War II, the Soviet Union invaded the Kingdom of Bulgaria and installed a Communist puppet government loyal to Joseph Stalin. The new regime began to enact laws to destroy religious institutions and beliefs. On 6 August 1946, the Pope appointed Eugene Bossilkov Apostolic Administrator of the diocese of Nikopol (which corresponds to the entire territory of Bulgaria). Amidst the anti-religious propaganda of the Communist regime, he made great efforts to persuade his congregation to remain faithful to the Gospel of Christ and to the Pope. On 7 October 1947, he was ordained a bishop in the Ruse Cathedral. From 1949 the attitude of the State to religious institutes worsened – the government deported the Apostolic Delegate, seized Church property and suppressed the religious congregations. In 1952 the government initiated mass arrests of Church officials: the Bishop and twenty-nine other clerics and prominent Catholic laymen were arrested and jailed on 16 July. Bossilkov was charged with espionage and participating in an illegal Catholic organisation. The show trial opened on 20 September, and the verdict was read on 3 October – "death by shooting and confiscation of all property". The sentence was carried out on the night of 11 November, at 10:30 p.m., in the yard of the Central Sofia Prison. Bossilkov was buried in a mass grave and his body was never recovered.
Monsignor Bossilkov was beatified on 15 March 1998 by Pope John Paul II in St. Peter’s Basilica in the Vatican. He was the first martyr of the Communist regimes in Eastern Europe to be beatified by the Catholic Church.