Chinese authorities say a troubled 22-year-old man fashioned a deadly bomb that killed eight people on Thursday at the front gate of a kindergarten. The man, identified only by his surname, Xu, was found using security footage and DNA collected at the scene. He was killed in the blast, which struck at about 4:50 p.m. while families waited to pick up students. Sixty-five people were injured in the explosion. Xu’s residence was also filled with materials for making a homemade bomb, investigators said.