Where do you suppose the term "massacre" to describe this event came from

I just answered this question. Here's my

There was an engraving that shows the British Soldier indiscriminately firing towards the crowd of colonists. 

The Boston Massacre in 1770 was termed a massacre based on the engraving.  However, the engraving did not explain nor show that prior to the soldier shooting at the crowd, they were being attacked by the crowd of colonists. The soldiers were pelted with rocks and snowballs and fearing for their lives, they defended themselves when they shot at the crowd. Unfortunately, their shooting went into extreme which resulted to mass casualties.