CHENNAI: A 27-year-old autorickshaw driver died after four men attacked him with a knife near the U-turn on Ramakrishna Mutt Road in Raja Annamalaipuram on Tuesday evening. Abiramapuram police arrested all four suspects within hours and altered the case from attempted murder to murder.The deceased, Sivakumar, son of Ayyappan, lived in KVB Garden in Raja Annamalaipuram. He was sitting inside his autorickshaw when the four men, who arrived on two-wheelers, attacked him and fled.Sivakumar was initially admitted to Govt Royapettah Hospital. As his condition required further treatment, he was shifted to Rajiv Gandhi Govt General Hospital, where he later succumbed to his injuries.Based on a complaint lodged by his mother, Abiramapuram police registered a case. The arrested suspects were identified as Loganathan, Veera, Ajith and Ramu.Preliminary investigations revealed that Sivakumar and Loganathan had a previous enmity following a physical altercation about three years ago. Police suspected that Loganathan had carried out the attack with the help of his associates.All the four arrested men were produced before a magistrate court and remanded in judicial custody on Wednesday.