This research sheds light on how one particular group of young people, Columbiners, use social media to build and maintain a sense of community. Through a content analysis of 200 Instagram posts containing a school shooting fandom hashtag, or #Columbiner, and drawing on both Critical Youth Studies and Sense of Community Theory, this research demonstrates how Columbiners use their hashtag to create a sense of community on Instagram, to explore what it means to be young and cool, and to make sense of the problems that shape their social world, including school shootings. Exploring how this particular group of young people engage with each other on social media provides researchers an opportunity to listen to young people as they develop their understandings of topics as seemingly mundane as homework to those as serious as school shootings.