What was the colonists objective in gathering at Lexington?

There was a town in Lexington where the colonists would be, but when the British came nobody thought a battle would actually happen. The Battle of Lexington is not really a battle, although it does mark the start of the American Revolution. The colonists and the British troops got confused when a random gunshot sprung out, making the British attack. This lead to numerous deaths among colonists but the rest fled.