Why did the battles of Lexington & Concord erupt in New Hampshire after Paul Revere warned the British?

Revere did not really do anything. He was one of 20 riders who set out that night. Only prescott returned. After Revere left he stopped at a tavern for a beer. Some redcoats walked in the tavern and another rider engaged them. Revere ran home. He really did not "warn" anyone.