Massacre

A massacre is an event of killing people who are not engaged in hostilities or are defenseless. It is generally used to describe killing of civilians en masse by an armed group. The word is a loan of a French term for "butchery" or "carnage". Other terms with overlapping scope include war crime, pogrom, mass killing, mass murder, and extrajudicial killing.

Quotes

 * I know of no word in the English language other than massacre which better describes the wanton slaughter of thousands of defenseless men, women and children.
 * Kenneth Keating,   quoted in Bass, G. J. (2014). The Blood telegram: Nixon, Kissinger, and a forgotten genocide.