Paul Seo Yu-hyeong was a relative of Peter Seo Tae-sun who died a martyr in Sangju in 1867. His family had moved earlier to Gyeongsang province and lived there. When the Byeongin Persecution broke out in 1866, his family was living in Mojeon, Jeomchon, Gyeongsang-do (present-day Jeomchon-dong, Mungyeong-si, Gyeongbuk).

Policemen were searching for Catholics everywhere after the Byeongin Persecution began. They eventually raided Mojeon around October 1866 after the fall harvest. At that time, Paul was arrested along with his wife Magdalene Seong Jae-chu, his seven-year-old daughter, his three-year-old son Seo Sun-bo, and servants. The policemen also went to the house of Paul’s elder brother and arrested his elder brother’s wife Lucy Pak. Finally, they also arrested Mr. Bang, a catechist who lived nearby.

Paul was shortly taken to the Sangju military base along with others. However, on the same day that his servants were released, his wife Magdalene was released along with his children because the children were young. Meanwhile, Paul had to undergo interrogation and torture along with his other family members and Mr. Bang the catechist. After that, they were put in prison and all of their assets were confiscated. It was said that his wife Magdalene supplied them with food and clothes from outside the prison.

One day Mr. Bang the catechist decided to escape from prison and suggested that Paul go with him. However, Paul declined his suggestion by saying, “If I miss such a good opportunity for me to die a martyr, when can I have a chance again to offer my life for God?” As a result, only Paul was left in the prison along with his elder brother’s wife Lucy, Augustine Kim and Peter Seo Tae-sun who had been arrested in Hansil, Mungyeong and then had been transferred to Sangju.

They started to execute Catholics in the prison of the Sangju military base one by one. As a result, Paul Seo Yu-hyeong was severely beaten once again along with his elder brother’s wife Lucy, Augustine Kim, Peter Seo, and others on January 23-24, 1867 (December 18-19, 1866 by the lunar calendar). Then, he died a martyr by hanging.