A 36-year-old sub-inspector hasbeen bookedfor allegedly beating a man who accompanied a complainant in a kidnapping case to Mahim police station here, an official said on Sunday.The incident took place on Friday when sub-inspector Gahininath Satav was on night duty.Ganesh Jalgaonkar (55), a Western Railway employee residing in Mahim Causeway area, went to Mahim police station along with his neighbour Nadeem Sheikh to find out about the progress made in Sheikh's complaint of his two minor children going missing, the police official said.Sheikh had filed a police complaint after his children went missing from home on Wednesday.When Sheikh and Jalgaonkar went to the police station on Friday around 3 am, Satav asked them why they were sitting there. The two men told him they had come to enquire about Sheikh's missing children, the official said.Jalgaonkar then allegedly abused Satav, following which the latter slapped him, he said.Satav also asked a constable to lock Jalgaonkar in a room where he again allegedly slapped him. In the process, Jalgaonkar's head hit a table, causing bleeding, the official said quoting the man's complaint.Jalgaonkar was later shifted to Bhabha Hospital in Bandra where a medical examination revealed a head injury and swelling on his ears and cheeks, he said.A report about the incident was sent to senior Mumbai Police officials, following which an FIR was registered against Satav under Indian Penal Code Section 336 (act endangering life or personal safety of others), he said.Besides, Jalgaonkar was also bookedunder IPC Sections 353 (assault or criminal force to deter public servant from discharge of his duty), 309 (attempt to commit suicide), 504 (intentional insult with intent to provoke breach of peace), 506 (criminal intimidation) and provisions of the Maharashtra Police Act, the official said."Further action will be taken after a proper investigation in the case. No arrest has been made so far. A report about the incident has been sent to senior police officials. Satav is still continuing his duty at the Mahim police station," he said.