The phrase "brutal massacre" refers to a violent and extremely cruel event where a large number of people are killed or harmed in a savage and merciless manner. Full definition
«In Jos, Plateau state, the protest ended peacefully as youths marched through the streets reminding the public how brutal the massacre carried out by the military in Zaria, Kaduna state was». (securitykingng.org)
Unfortunately... yes, there is a caveat... the filmmakers behind Brutal Massacre: A Comedy were not nearly brutal enough in the editing room. (horror.com)
In the brutal massacre of the population that followed, only the Christians were spared, as they were a favored group. (religion-online.org)