RAMANATHAPURAM: A 20-year-old mentally ill man beheaded his two-year-old niece and threw her head into a pond in Emaneswaram village near Paramakudi on Thursday morning. Ramanathapuram SP G Chandeesh told TOI that the man was under medication for bipolar disorder, but they were examining all aspects of the case.The victim, D Lemoria, who turned two in Feb, was the daughter of Desingu Raja, 32, and D Daisy, 28. Police said she was playing with her 13-year-old cousin sister near her house when the accused, M Sanjay, arrived and pulled her away from the play area. He took her to the backyard of his house, located about 50-100 metres away, and severed her head with a knife kept there.Thereafter, he walked away with the head and threw it into a nearby pond before escaping.It was her cousin who discovered the girl’s mutilated body after some time and alerted her family. The child’s body was retrieved by police and taken to Paramakudi Govt Head Postmortem Hospital for further examination. Authorities launched a search for the suspect immediately and caught him by afternoon. He was being questioned at the police station.“Preliminary investigations reveal that the accused has bipolar disorder and was under medication. We are providing all necessary medical and legal support to handle the situation. The suspect is in custody for further questioning but seems mentally unstable while answering,” SP Chandeesh said.