Why did you find the soilders guilty on the murder charge of killing people in the boston masacre

Because they shot their weapons at civilians.

Soldiers were found guilty of murder in the Boston Massacre because they fired their guns at the crowd and killed 5 colonists.

Explanation:

The Boston Massacre happened on March 5, 1770, on King Street, Boston. It started as a conflict between some colonists and one British soldier who was guarding the King's money that was inside the Custom House. These colonists attacked him with snowballs, stones and ice because of their anger towards the laws and taxes that the British had imposed on them.

The conflict quickly got worse and more soldiers came to the scene hitting the colonists until one of them opened fire. Five of them were killed and this caused greater anger towards the British government, resulting later in the American Revolution.  

it affected it because the kingdoms (with trade) slowly got richer and richer.