Capt. Tun Myat Aung leaned over the hot pavement in Yangon, Myanmar’s largest city, and picked up bullet casings. Nausea crept into his throat. The shells, he knew, meant that rifles had been used, real bullets fired at real people.

That night, in early March, he logged on to Facebook to discover that several civilians had been killed in Yangon by soldiers of the Tatmadaw, as Myanmar’s military is known. They were men in uniform, just like him.

Days later, the captain, of the 77th Light Infantry Division, notorious for its massacres of civilians across Myanmar, slipped off base and deserted. He is now in hiding.