No one led the battle. It was an event that just happened. To this day history doesn't report who fired the first shot in Lexington. The 77 colonist of Lexington were waiting on the village green...
The battles were two major battles on the same day. Lexington happened first on the morning April 19, 1775 when the British patrol marched into the town and met 77 colonial men waiting for them....
In the battle of Concord and Lexington, the Patriots were outnumbered but after the battle, they ambushed the British soldiers. Though they lost, they felt proud that they killed many on the ambushed.