Animal (and human) sacrifices  have been a terrible reality of many cultures for thousands of years. Below are excerpts from Wikipedia about the subject.

Animal sacrifice is the ritual killing of an animal as part of a religious event.  It is practiced as an act of obedience and as a means of appeasing a god or gods and changing the course of nature.  Animal sacrifice has [been a part of] almost all cultures [to include the] Hebrews … Greeks… Romans … Ancient Egyptians [and] Aztecs.

[Human sacrifice has[also] been practiced by many cultures. The reasons include:

Idol worship.]

…death of a king, high priest or great leader; the sacrificed [humans] were supposed to serve or accompany the deceased leader in the next life…

…times of natural disaster. Droughts, earthquakes, volcanic eruptions, etc. were seen as a sign of anger or displeasure by deities, and sacrifices were supposed to lessen the [god's anger]…

The Aztecs practiced human sacrifice on an unusually large scale; a sacrifice [was] made every day to aid the sun in rising… the dedication of the great temple at Tenochtitlán [required the sacrificing of thousands [of people]….

The Phoenicians of Carthage were reputed to practice child sacrifice…, there is archaeological evidence of large numbers of children’s skeletons buried … with sacrificial animals.

Human sacrifice still happens today as an underground practice …Human sacrifice is no longer officially condoned in any country, and [is now] regarded as murder.