Twitter and other social platforms have become important communication channels during crises. While research into crisis informatics and social media is growing, the rarity of terrorist attacks in developed, Western countries complicates analysis of these specific events. To address this gap, we explore social media response to three terror events: the 2013 Boston Marathon Bombing, the 2014 Sydney Hostage Crisis, and the 2015 Charlie Hebdo Shooting. We show that, while these events do not significantly impact general Twitter usage, those users who are discussing the event behave in predictable ways across all three events. Such behaviors include increased references to the event and use of retweets, hashtags, and URLs. Furthermore, local news affiliates and law enforcement agencies (if present on social media) emerge as central actors in the networks.