India, July 1 -- A 21-year-old man murdered a fellow prisoner, who had allegedly raped his sister and pushed her to suicide in 2014, at Delhi's Tihar prison on Monday, investigators said citing initial probe, and added it was a revenge killing he had been planning since July 2018 when he was arrested for murder.

The 21-year-old attacked Mehtab, 27, with a sharp metal strip and stabbed him in the neck multiple times. Mehtab was rushed to the nearby Deen Dayal Upadhyay hospital, where he was declared brought dead.

Mehtab had been in prison since 2014 for the alleged rape, an investigating officer. "In July 2018, the 21-year-old was arrested for a rickshaw driver's murder. He learnt Mehtab was also in prison. They were lodged in different ...