A mentally ill person has beaten a man to death in Belbari of Morang district on Tuesday night. The deceased has been identified as Hari Bahadur Karki (40), of Belbari Municipality. The incident took place when Ashish Rai (29), of Belbari Municipality, thrashed Karki. Police Inspector at the Area Police Office, Belbari, Meghraj Thapa, said that Karki, who received deep injury on his head from the thrashing, died while undergoing treatment at Dharan-based BP Koirala Institute of Health Sciences.