Patna, March 27 (IANS) A mentally challenged man was beaten to death by a mob in Bihar's Purnea district on Sunday after he stabbed to death an old man, police said.

The attacker, in his mid-30s, was lynched at Jiyanganj area, about 350 km from here.

"The mob attacked and beat to death the mentally challenged man after he stabbed to death an old man following heated exchange of words," said a district police official.