Which colonial action of the early 1775 concerned the British military leaders in Boston?

In early 1775, the British military leaders in Boston were particularly concerned about the escalating tensions following the actions of colonial militias, especially the stockpiling of arms and ammunition in places like Concord. The colonial resistance was growing more organized, exemplified by the formation of the Continental Congress and the increasing confidence of militias. The British viewed a planned march to Concord to confiscate these supplies as a direct challenge to their authority, leading to the outbreak of hostilities at Lexington and Concord in April 1775. This marked a significant turning point in the American Revolution.