In a new video, a man claiming to be Boko Haram leader Abubakar Shekau took responsibility for the massacre in Baga, Nigeria, in early January, claiming that God told them to do it. Local officials and human rights groups put the death toll at 2,000, but the Nigerian army reported only 150 deaths.

Shekau also threatened more attacks in Nigeria. The group had seized the nearby army base after soldiers fled. Militants displayed weapons from the army base, with Shekau stating the arsenal was “enough to annihilate Nigeria.”

The multiple-day attack was the deadliest by the group. A witness told Amnesty International that militants murdered a woman in labor.

“[H]alf of the baby boy is out and she died like this,” he described.

Doctors Without Borders is currently treating survivors in Maiduguri, the capital of Borno State. The United Nations claimed over 11,000 people have since fled to Chad. Human Rights Watch and Amnesty released before and after satellite images of Baga and Doro Gowon, which show the attack demolished over 3,700 structures.

“These detailed images show devastation of catastrophic proportions in two towns, one of which was almost wiped off the map in the space of four days,” reported Daniel Eyre, Nigeria researcher for Amnesty. “Of all Boko Haram assaults analysed by Amnesty International, this is the largest and most destructive yet. It represents a deliberate attack on civilians whose homes, clinics and schools are now burnt out ruins.”