On Aug. 27, Aung Thein Mya arrived in the Rohingya section of the village at around 9 a.m. accompanied by a group of soldiers, witnesses said, and stole a widow’s cow. What happened next was described by six witnesses, including Shom Khatun, the cow’s owner.

Aung Thein Mya had the cow slaughtered and the meat cooked in a large pan as a curry. Just hours before the violence began, Aung Thein Mya sat down with his comrades and ate the curry in view of the people he was about to massacre.

The killing started around 1 or 2 in the afternoon, witnesses said.

Abdul Hashem, a 73-year-old religious leader, said he was with a group of men at the mosque before afternoon prayers. Karima Khatun, 20, said she was cleaning the kitchen when she saw soldiers approaching her home. Roushon Ali, 48, said he heard someone give an order for everyone to come out of their houses.

Aung Thein Mya seemed to be helping soldiers identify targets, witnesses said. Mr. Hossain, the administrator’s former subordinate, said he saw Aung Thein Mya talking on his phone immediately before the shots rang out.

“We are ready on this side,” he said he heard Aung Thein Mya say. “Come and shoot soon. Kill. Kill them all.”

“After that they started shooting,” Mr. Hossain said. He watched the carnage, he said, while hiding in a pond with seven other people. “People were dying. Injured people were screaming in pain. They were being burned alive. Some people were hiding in the hills, some were in the ponds, some were in the bushes, some were in the toilets.”

Fir Mohammad, 16, said he bolted out the back door when soldiers rushed into his house. Almost immediately, he was hit by a bullet, which entered his back and burst from his chest.