The incident began on King Street when a young wigmaker's apprentice named Edward Garrick called out to a British officer, Captain John Goldfinch, that he was late paying his barber's bill. Goldfinch had in fact settled his account that day but did not reply to the boy. When Garrick remained quite vocal in his complaints an hour later, the British sentry outside the customs house, Private Hugh White, called the boy over and clubbed him on the head. Garrick's companions yelled at the sentry, and a British sergeant chased them away. The apprentices returned with more locals, shouting insults at the sentry and throwing snowballs and litter.

White sent a messenger to the Main Guard for reinforcements. The Officer of the Day, Captain Thomas Preston, dispatched a corporal and six privates, all grenadiers of the 29th Regiment of Foot, and followed soon after. The mob grew in size and continued throwing stones, sticks, and chunks of ice. A group of sailors and dockworkers came carrying large sticks of firewood and pushed to the front of the crowd, directly confronting the soldiers. As bells rang in the surrounding steeples, the crowd of Bostonians grew larger and more threatening.

In the midst of the commotion, Private Hugh Montgomery was struck down onto the ground by a thrown club. He fired his musket into the air and—as he later admitted to one of his defense attorneys—yelled "Fire!" All but one of the other soldiers shot their weapons into the crowd. Three Americans—ropemaker Samuel Gray, mariner James Caldwell, and a mulatto sailor, Crispus Attucks—died instantly. Seventeen-year-old Samuel Maverick, struck by a ricocheting musket ball at the back of the crowd, died the next day. Thirty-year-old Irish immigrant Patrick Carr died two weeks later. Six more men were injured. To keep the peace, the next day royal authorities agreed to remove all troops from the center of town to a fort on Castle Island in Boston Harbor.