The word "prey" is used when describing an animal or a human being that is attacked or assaulted by another animal or human. Notice that this word is different from "pray," which is spelled with an "a."
Wolves prey upon rabbits.
Snakes prey on mice.
A story in the newspaper tells of an incident in which a salesperson preyed upon elderly people and cheated them out of millions of dollars. Eventually he went to jail.
Men who prey upon vulnerable women should be ashamed of themselves.
People who appear to be gullible are preyed upon by those who lack a sense of morality and decency.
The word "prey" is also a noun:
Snakes go after live prey.
The salesperson marked the customer as easy prey. (It would be easy to make sale to this customer.)
Without a healthy supply of prey, certain carnivorous animals will starve to death.