The event that led to the Boston massacre was due to the tension produced by the military occupation of Boston, when a group of soldiers began firing at a group of nobles who protested against the increase in rates by England.
Although prior to all this was the Boston tea party.
Where the port of Boston had to be closed for weeks after the tea party, due to the bad smell that caused the large amount of tea poured into the port.
The answer is: .The protest of noble against the increase of the rates, and the party of the Boston's tea.