MANILA — The drug raid ended like so many others in the Philippines, with all the suspects shot by the police.

But one of them, Efren Morillo, a 28-year-old fruit and vegetable vendor, did not die.

As the only known survivor of a so-called buy-bust operation, Mr. Morillo has provided a chilling first-person account that challenges the government’s assertion that the thousands of suspects killed in President Rodrigo Duterte’s antidrug campaign were killed by the police in self-defense. And his testimony lies at the heart of the first court case to challenge that campaign.

According to his sworn affidavit, none of the five suspects were drug users and none were armed.

The police took two of them, including Mr. Morillo, inside a house, handcuffed, Mr. Morillo said. Three others were lined up at a clearing near a ravine, ordered to kneel, their hands tied behind their backs.

There was begging and crying as the police shot each man at close range, Mr. Morillo said.

“Thoroughly frightened that I might be shot again, I closed my eyes and played dead,” he said. As he lay on the floor bleeding, he said, he overheard the police officers talking about planting guns and drugs because they had found none there.