An armed man burst into the Cathedral of Resurrection, the main cathedral of the Yuzhno-Sakhalinsk diocese, Sunday afternoon and made several shots, Interfax was told at the local diocese.
"A nun working in the cathedral and a parishioner who is now being identified died of wounds in the cathedral," Interfax was told.
Six other people were wounded.
A team of detectives and investigators is working at the scene. The gunner has been caught.