A new video from Nigeria's Boko Haram extremists shows gunmen shooting civilians lying face down in a dormitory, and a leader saying they are being killed because they are "infidels".
There are so many corpses that the gunmen have difficulty stepping to reach bodies still twitching with life.
"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," the group leader says in a message.
"From now, killing, slaughtering, destructions and bombing will be our religious duty anywhere we invade."
The video appeared two days after fleeing villagers reported the extremists were rounding up elderly people and killing them in two schools in Gwoza, in northeast Nigeria.
The setting of the latest video is a school dormitory which the leader says is in Bama, a town 60km north of Gwoza.
Students and schools are frequently targeted by Boko Haram, which means "Western education is sinful".
Previously, the militants had told villagers they would kill only enemies and wanted people to live peacefully in the area they have dubbed an Islamic caliphate, a large swath along Nigeria's northeastern border with Cameroon.
Thousands of people have been killed and 1.6 million driven from their homes in the insurgency that is spilling into Cameroon, Chad and Niger.