The balloon seller, identified as Salim (40), son of Khamaruddin and a resident of Tofiya village, Kannauj district in Uttar Pradesh, died on the spot.
"The incident took place after 2.15 pm on the school grounds during school lunch hours when three people who were using helium cylinders to fill air balloons got injured after the cylinder and the balloon burst," Surguja Superintendent of Police Sunil Sharma said on Thursday.