TikTok is full of entertaining cat videos, humorous dances, and yes, even challenges -- the famed ice-bucket challenge has returned and is promoting mental-health support. But now a dangerous TikTok challenge is spreading through the short-form video app and through schools across the US.

Another dangerous TikTok challenge has prompted urgent warnings from school districts and law enforcement agencies nationwide, and led to a 15-year-old New Jersey student being charged with arson.