US Patriots were protesting the occupation of their city by British troops sent there to enforce the payment of a tax levied on the colony by a British Parliament which had no US representation.

British troops fixed their bayonets and stood guard outside the Customs House. The colonist started to throw snowballs and other objects and the troops opened fire. Five Patriots were killed - Crispus Attucks, Patrick Carr, Samuel Gray, Samuel Maverick, and James Caldwell.

The British soldiers were put on trial. Patriots John Adams and Josiah Quincy agreed to defend the soldiers. When the trial ended in December 1770, two British soldiers were found guilty of manslaughter and had their thumbs branded with an "M" for murder as punishment.

This incident was named the Boston Massacre by a Patriot group campaigning against the British imposed Stamp Act. It was used as a call to arms by Patriots for the removal of the British ands some claim the five casualties were the first deaths of the American Revolutionary War.