POLICE believe a man who committed suicide by jumping on to the track at Causeway Bay MTR on Tuesday had earlier killed his girlfriend in a Wan Chai hotel. Detective Chief Inspector Philip Bouttle said police believe Lam Yat-chor, 36, hit his girlfriend, Ng Wai-yee, 23, on the head with the porcelain lid of a lavatory cistern wrapped in a towel. Results of a post mortem examination revealed the woman had died of brain damage. Police have not ruled out the possibility the incident arose out of an argument over a failed love affair. Police inquiries revealed that Ng moved out from a flat in Shun Yung Street, To Kwa Wan, three days ago. Inspector Bouttle said police were having difficulties in finding out the man's background as his uncle who identified his body had not seen him for seven years. Ng's body was found by a cleaner at the San Diego Hotel in Morrison Hill Road about 6 pm on Tuesday. An unsigned note saying someone wanted to be buried with the woman was found on the dressing table. Three hours earlier, Lam died under a train at Causeway Bay MTR station. He was found to be the person who booked into the hotel when he arrived with his girlfriend about 6.40 pm on Monday.