Although researchers know much about the causes of aggression, they know surprisingly little about how aggression leads to violence or how violence is controlled. To explore the microregulation of violence, we conducted a systematic behavioral analysis of footage from closed-circuit television surveillance of public spaces. Using 42 incidents involving 312 people, we compared aggressive incidents that ended in violence with those that did not. Behaviors of antagonists and third parties were coded as either escalating or conciliatory acts. Results showed that third parties were more likely to take conciliatory actions than to escalate violence and that this tendency increased as group size increased. This analysis revealed a pattern of third-party behaviors that prevent aggression from becoming violent and showed that conciliatory behaviors are more successful when carried out by multiple third parties than when carried out by one person. We conclude by emphasizing the importance of collective third-party dynamics in understanding conflict resolution.