XUZHOU, China — On most days, the pageant of parents jostling to pick up their children began at 4:45 p.m. on the tree-lined streets outside the Chuangxin kindergarten. Car horns blared. Parents whistled and waved their arms, holding boxes of juice and cookies, as the children emerged.

But on Thursday, the rite turned into a scene of carnage, as an explosion outside the school’s main gate killed eight people and injured 65 others. Children, their faces covered in blood, screamed on the sidewalk. Parents lay on the street, some unconscious and others pleading for help.

“Suddenly, we were in a nightmare,” said Bo Li, 62, who was waiting to pick up his 4-year-old granddaughter. “The world didn’t seem real.”

Chinese investigators on Friday pointed to a suspect in the explosion, Xu Taoran, 22, a university dropout who had written violent screeds against parents and children. The police recovered explosive materials in the home of Mr. Xu, who died at the scene.