Kent State University, May 4, 1970. The Ohio National Guard fired on students, killing four and wounding three, including Jeffrey Miller, pictured here. The students were unarmed and presenting no immediate threat to the Guard, who had were carrying loaded weapons as they initiated clashes with students that day.
See comments at
(Notes on) Politics, Theory, Photography
There is an extended discussion of this photograph and its derivatives in Robert Hariman and John Lucaites, No Caption Needed.
Kent State May 4 Center
May 4 Collection, Kent State University Library
Kent State Shootings at Wikipedia
Kent State / May 4 1970 at tripod
May 4 Archive, J. Gregory Payne
(photograph: John Filo)