Michael W. Richter Ridgefield , Conn. , Oct. 3 , 2006 To the Editor : In the last five and a half weeks , five schools in the United States and Canada have suffered the invasion of gunmen : Aug. 24 , Essex , Vt. ; Sept. 13 , Montreal ; Sept. 27 , Bailey , Colo. ; Sept. 29 , Cazenovia , Wis. .