Boston's early history is anything but peaceful, really. Puritans hanged women that dared to have differing opinions about religion. Efforts to convert natives often turned sour. Even by the start of the American Revolution, Bostonians were a bit fighty. The Boston Massacre was more of a brawl than a massacre. However, there were always reasons behind the violence - some good, some bad. In the case of the Boston Bread Riot, the reasoning was sound enough.
In the early 1700s, Boston was still just a town that relied heavily on its ports. It was actually quite smaller and surrounded by wetter land and water that is reclaimed land today. Therefore, farming was not really possible, so the town was taking in its grain from other places and relying on merchants (some of which were the colonial version of big business) to sell them grain. Unfortunately for the lower classes, merchants decided that not only would they hoard grain to make the prices go up, they would also take the limited amount of grain and export it because that paid better.
On top of the grain issues, the colonies were caught up in the French and Indian Wars. Around the time of the Boston Bread Riot and the events leading up to it, Queen Anne's War (the second of the French and Indian Wars) was the problem. The lack of money, rising prices and limited availability of grain, along with some other foodstuffs, was at crisis level by 1709. By 1710, Boston bared its teeth.
One of the richest merchants in town became the target of a relatively small riot in 1710. One of his ships suffered some damage, but that was the extent of it. The following year saw another small riot as hardships got harder with a large fire in the town. Finally, in 1713, enough was enough. More than 200 people gathered on the Boston Common to protest the continued scarcity and high prices of grain. They went after the same merchant who fell victim to attack in 1710.
According to "A People's History of the United States" by Howard Zinn, Kathy Emery and Ellen Reever, a member of the crowd shot the Lieutenant Governor while they were looting a merchant's stock. However, finding another source for this claim has proven difficult. Moreover, biographies of William Tailer, who would have been the man shot, mention nothing of the sort.
In the end, it was a mild riot in terms of damage, but it did some good. Policies were soon put into place to keep grain in the area when there were shortages. It also locked prices so they would not inflate too much. It did not solve all of Boston hunger problems, but it was a start.