Black July is the commonly used name for the pogroms starting in Sri Lanka on July 23, 1983. It is estimated that 1,000 Tamil people were killed, tens of thousands of houses were destroyed, and a wave of Sri Lankan Tamils left for other countries. The riots occurred following a deadly ambush by a Tamil militant Liberation Tigers of Tamil Eelam which killed 13 Sri Lanka Army soldiers.
Black July is generally seen as the start of full-scale armed conflict between Tamil separatists and the Sinhalese-dominated government of Sri Lanka http://en.wikipedia.org/wiki/Black_July
During the black july many innocent tamils were attacked by extremist singhalese elements, that helped LTTE to recruit more people into thire organization,I think it is most unfortunate incident that happend in Sri lankan history,