Dhanbad, Dec. 1 :     Principal judge of a labour tribunal Bibhuti Bhushan Chatterjee was murdered by a watchman early this morning near the Coal Mines Provident Fund (CMPF) Colony. The killer, identified as Shibu Rai (50), later surrendered at the Dhanbad Sadar police station and confessed to his crime. Chatterjee, a retired district judge from Bankura and a senior officer of West Bengal judicial services, was posted here for the past two years as the principal judge-cum-presiding officer of the tribunal. He was living in one of the rooms of the tribunal because of the non-availability of official residence. Superintendent of police Anil Palta said Shibu, who was mentally deranged, had sought Chatterjee?s help in obtaining bail for his son, accused in a murder case. Palta said Shibu had approached Chatterjee late last night and asked him to contact the police to plead on behalf of his son. Chatterjee did not respond to his request in view his mental status. Shibu broke into his room early this morning and bludgeoned him with a boulder. The judge sustained grievous head injuries and died on the spot. Shibu, subsequently tried to set the victim?s body ablaze. The sweeper discovered the body and raised an alarm. Around 10 am, Shibu surrendered to the police. Palta said the police have already informed the victim?s family at Raghunathpur in Purulia district.