We examine the effects of mass transit strikes on criminal behavior in Los Angeles County utilizing a unique dataset of reported crimes between 2000 and 2007. Geocoded location and time information pertaining to each offense accommodates a fine grained difference-in-differences panel data analysis. We find that in locations affected by the strike, aggravated assaults rose by 18.7% while aggregate property crimes increased by 5.7%, relative to their mean. This increase in crime was disproportionately larger in lower income neighborhoods, which report higher usage of mass transit, suggesting local isolation of both criminals and victims as a mechanism. (JEL J52, K42, K31).