The class photo is a picture of happiness, with dozens of teenagers in crisp blue-and-white uniforms smiling brightly at the camera ahead of a weekend Bible camp in the picturesque village of Jono Oje, in the tropical countryside of northern Sulawesi.

Hours after it was taken, many of the students were dead, trapped and suffocated in a church that was wrenched from its foundation and driven more than three miles away by a wave of muddy sludge triggered by the earthquake that struck the Indonesian island last week.

Hala Tawasa, 50, lived beside the church and witnessed the horrific scene as her son carried her to safety from the ruins of their home.

“We had run out of the house when it began to…