Harpreet Singh alias Happy Singh, convicted in an abduction case and serving life term in a prison, was Monday killed in an attack by a fellow inmate, an official said.
Singh was convicted in the 2001 abduction of Khadim director Partha Roy Burman and was serving time in the Presidency Correctional Home in Kolkata.
"Singh was a fitness freak and today while he was doing yoga, a fellow inmate who is mentally unstable, attacked him with a brick hitting repeatedly on the head. He was shifted to M.R. Bangur hospital where the doctors pronounced him dead," Inspector General (Correctional Services) Adhir Sharma told IANS.
Sharma said the doctors were in the process of issuing a formal death certificate although they had confirmed Singh's death.
He also said that a probe in the matter has been initiated and the attacker, identified as Nizamuddin, will be interrogated.
Singh, along with crime lord Aftab Ansari and three others, was convicted and sentenced to life in May 2009 for the abduction case.
The shoe baron was abducted in 2001 from the city and was later released after paying a ransom. His family members, witnesses in the case, had denied paying any ransom.