The Boston Massacre occurred on the evening of March 5, 1770. Captain Thomas Preston was the officer of the day. Based on testimonials of several witnesses at Captain Preston's trial, the events of that evening unfolded to turn it into an evening of blood shed.
That evening Theodore Bliss was standing and talking to the Captain. He states in his deposition that the colonists were throwing sticks and snowballs and taunting them to fire. One of the sticks thrown struck a soldier. The soldier was knocked down from the blow, and when he got back to his feet he grabbed his gun and fired into the crowd. That shot was then followed by several other shots, but Captain Preston did not give the order to fire.
Richard Palmes was standing with his hand on the Captain's shoulder and speaking with him. He stated that he saw what appeared to be snow or ice hit a soldier. The soldier was knocked back and then he immediately fired his weapon then more shots followed after the first. He did hear the word fire, but could not say who gave the order. He was looking at the soldier who fired the first shot.
Jane Whitehouse, whom was standing about three yards away stated, she was sure Captain Preston did not give the order to fire. The man she saw and heard was behind the soldiers dressed in dark clothes. He put his hand on their backs and said "fire, by God I'll stand behind you."" (Bostonmassacre.net).
James Woodall whom was standing a few yards away stated, he saw one soldier get knocked down and dropped his gun. The soldier got up and fired. After that shot he saw a man dressed in "blue or black clothes with gold trim."" (Bostonmassacre.net) This man put his hand toward the soldiers' backs and said, "fire, by God I'll stand by you,"" (Bostonmassacre.net) then more shots rang out.
Based on all this testimony, the Boston Massacre occurred because of several elements. A few young men were taunting the sentinel at the Boston Custom House to fire upon them.