A private helicopter on a joyride crashed and erupted into a fireball, killing the pilot and injuring three others, at an isolated spot in the Mumbai suburb Goregaon on Sunday.The helicopter, a Robinson R44 belonging to Aman Aviation Pvt Ltd, was on a sight-seeing flight over Mumbai when it suddenly crashed inside the forested Aarey Milk Colony and caught fire around 12.15 p.m., said the BMC Disaster Control.According to witnesses, hundreds of people from nearby tribal hamlets inside the Aarey Milk Colony and some other settlements rushed to help the victims even as fire tenders rushed to the spot.People and police personnel extricated the victims from the burning chopper and rushed them to the Seven Hills Hospital in Andheri East.While pilot Prafulkumar Mishra was declared dead, a co-pilot and two passengers including a woman are reported to be in critical condition, a hospital official said.