Final answer:
The event that started the Boston Massacre was a confrontation between angry colonists and British soldiers in Boston on March 5, 1770. The colonists began throwing snowballs at the soldiers, which escalated into a skirmish and gunfire, resulting in the death of five colonists.
Step-by-step explanation:
The event that started the Boston Massacre was a confrontation that took place on March 5, 1770. A crowd of angry colonists gathered to harass British soldiers at the local customs house in Boston. The colonists started throwing snowballs at the soldiers, which led to a skirmish and gunfire. As a result, five colonists were killed, and this event became known as the Boston Massacre.