Unfortunately, I have only Slavonic text from the Patericon by Dmitry Rostovsky (https://azbyka.ru/otechnik/Dmitrij_Rost ... 0#note1726) where he is named "Иаков Постник". His memory celebrates in March, 4 according to Julian calendar.
The story tells that saint Jacob spent 10 years crying out the murder and rape he made being already saint (that information probably should help in searchings). I would be grateful for finding at least an English version of that text.
