Why did colonists clash with the British at Lexington and Concord?

The British troops moved on Lexington and Concord in an attempt to seize a reported arms cache, and to attempt the capture of John Hancock and Samuel Adams. The information obtained by the British concerning the existence of the arms and the whereabouts of Hancock and Adams was good, but the two patriots were warned of the British movement by Paul Revere, and the colonials chose to stand and fight rather than retire, thus starting the war for American Independence.