The night of April 18 Paul Revere made his famous ride. The fighting started at 5am the next morning in Lexington and Concord. This is from an article I found.
Toward sunset the fatigued regulars returned to Cambridge in full retreat. At Watson’s Corner (2) (the present intersection of Rindge and Massachusetts avenues) Cambridge patriots lay in wait behind a pile of barrels at, but were surprised by flanking redcoats. John Hicks (3) and Moses Richardson of Cambridge and Isaac Gardner of Brookline were killed, as was William Marcy, a "simple-minded youth" who thought he was watching a parade. A marker at 2158 Massachusetts Avenue commemorates the skirmish.