A 51-year-old man was beaten to death by his son at their house in Vengathur village, Tiruvallur. The victim was identified as Balakrishnan, whose son Pandian, 28, is mentally unstable. . On Sunday,when a power cut occurred, Pandian asked his father to fetch a candle, but when Balakrishnan could not find one, a quarrel ensued. In a fit of rage, Pandian beat him to death.