What do you meant by term bloody sunday?
There could be two Bloody Sunday's you are talking about. The Russian Bloody Sunday or the Bloody Sunday that occurred in Ireland.
The Russian Bloody Sunday occurred on the 22nd January 1905, which is also known as the 1905 revolution. It occurred in St Petersburg and was led by priest Father Gapon. It was led to be a "peaceful protest" and was a call to the Tsar (King) at the time, Tsar Nicholas II (also the last Tsar of Russia, who got assassinated alongside his family in July 1918), to improve the working conditions of the peasants and to break the socio-economic conditions of the time period.
The goal of the event was to allow a Russian Parliament be in place and as I said before, improve working conditions through better hours (some Russian peasants were working up to 18 hours a day!) However, this was significantly unsuccessful, as historians believe this event had also led to the 1917 revolution, which ended Russia's participation in WW1 and also allowed the force removal of the Tsar (he ended up abdicating) and allow the Bolsheviks consolidate their power and through this, Russia turned into the USSR and then a communist country led by Joseph Stalin.
The Irish Bloody Sunday began on 30th January 1972 when British Soldiers had shot non armed civilians during a peaceful protest against internment. There were in total 14 deaths, in which 13 had died immediately after the event and one 4 1/2 months later. Many of the victims of Bloody Sunday were shot while assisting other victims and in total 28 innocent civilians were shot.
This event had caused a major increase in Catholic and Irish nationalist hostility towards the British army and exacerbated the conflict. Due to the results of Bloody Sunday, there was an increase in supporters of the Provisional Irish Republican Army (IRA)and there was a surge of recruitment into the organisation, especially locally.
Hopefully this helps :)