Rapid resolution of bugs is a key software engineering outcome. Past studies have shown that different aspects of developer interaction are associated with bug resolution times. However, such studies are predominantly correlational in nature; they do not establish causal connections between variables of interest. Software intensive systems play critical roles in nearly all aspects of our lives today. Thus understanding what causes software bugs to be resolved faster is of significant importance to the state of art and practice of software engineering. In this paper, we apply the Greedy Equivalence Search (GES) algorithm on real-world data from a large software development ecosystem to identify the causal influences on bug resolution times. Our results indicate that the amount of time needed to resolve a bug is affected by different types of interactions among developers, in addition to workload and experience of the developer owning the bug, and the number of developers working on the bug. The conclusions from our results can offer insights for researchers and practitioners on further causal investigations of software engineering outcomes.