Boko Haram released a video showing an apparent civilian massacre, according to CBS.

The Islamic extremist group, which has terrorized a large swath of Nigeria since April, continues to do so to fulfill their goal of establishing what they are calling an Islamic caliphate.

The group first came into the international spotlight when they kidnapped more than 270 schoolgirls from the town of Chibok in April.

A global movement on social media emerged, with the hashtag #BringBackOurGirls, calling for the release of the girls. Dozens escaped but more than 200 are still missing.

But Boko Haram has been terrorizing the region for about five years, and lately has been escalating their violence against residents of towns whom they deem infidels.

The recent video is the latest, showing dozens of men who were lying facedown on what appears to be the floors of a school as gunmen open fire on them.

"We have made sure the floor of this hall is turned red with blood, and this is how it is going to be in all future attacks and arrests of infidels," the group leader says in a message, according to CBS. "From now, killing, slaughtering, destruction and bombing will be our religious duty anywhere we invade."

The video also shows the group leader saying that prisoners should be held not killed, according to their prophet, but the group has decided on their own accord that now is not the right time to keep prisoners, CBS reported.

Boko Haram, whose name means "West is sinful," has killed dozens of people from towns in areas they are establishing their rule, and have drive more than a million out of their homes.

The Sunni jihadi group is enforcing strict Sharia law in the areas it overtakes, CBS reported.

There are reports of the militants kidnapping men from each town and killing them, as well as recently revisiting the town where the girls were kidnapped from and forcing the residents to flee.