In 2008, the U

In 2008, the U.S. Department of Homeland Security began using the term active shooter to refer to

A) a person who was actively engaged in killing or trying to kill people in a public area
B) mass killers who had killed at least two people in one location
C) a person who was actively trying to kill a group of people with a gun
D) a person who had killed three or more people with a gun