Shanghai's dazzling skyline became the backdrop for emotional venting Tuesday, as mourners paid respects to victims of a New Year's Eve stampede – and shouted that they want answers.

For more than two hours on a brisk and often wet morning, groups of family members and friends set flowers at a statue of a former mayor on the city’s famous riverfront Bund near where the 36 mostly young people were crushed to death.

"I...