What colonial action of early 1775 most concerned the british military leaders in Boston?

In early 1775, British military leaders in Boston were most concerned about the growing stockpiling of arms and ammunition by colonial militias, particularly in areas like Concord. The fear was that these militias were becoming increasingly organized and prepared to resist British authority. This tension culminated in the Battles of Lexington and Concord in April 1775, which marked the start of armed conflict between Britain and the American colonies. The possibility of widespread rebellion alarmed British commanders, prompting a more aggressive military response.