Comment: It was an ambush gone bad.

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.