Social Networking Site (SNS) is a great innovation of modern times. Facebook, Twitter etc. have become an everyday part of peoples' life. Among all SNSs, Facebook is the most popular social network all over the world. Bangladesh is no exception. People of Bangladesh use Facebook for social communication, online shopping, business, knowledge and experience sharing etc. As well as the various uses of SNSs, people sometimes find themselves involved in real life violence, provoked by some social media posts or activities. In this paper, we discussed some case studies in which real life violence is originated based on Facebook activities in Bangladesh. Facebook was used in these incidents intentionally or unintentionally mostly as a tool to trigger hatred and violence. We analyzed and discussed the real-world consequences of these virtual activities in social media. Lastly, we recommended possible future measurements to prevent such violence.