On May 4 , 1970 , thirteen students were shot , four of them fatally , at Kent State University in Ohio by National Guardsmen as they protested the U.S. involvement in the Vietnam War and U.S. incursions into Cambodia . As a show of sympathy for the dead students , Republican Mayor of New York City John Lindsay ordered all flags at New York City Hall to be flown at half-staff the same day
thirteen students were shot
Kent State shootings
Hard Hat Riot