The 1947 Mirpur Massacre was the killing of thousands of Hindu and Sikh refugees in Mirpur of today's PoK, by armed Pakistani tribesmen and soldiers during the First Kashmir War. It occurred on and after November 25, 1947.
On this day Mirpur Balidan Divas is observed by the PoK Refugees in Delhi Jammu, Sunderbani, Poonch, Udhampur and other parts of India where the community is settled.
Links:
https://en.wikipedia.org/wiki/1947_Mirpur_Massacre
http://sikhsangat.com/index.php?/topic/69597-mirpur-1947-–-the-untold-story/