Police have named the man killed in an incident at Auckland Prison on Thursday.
Rotorua man Blake John Lee, 25, died after an assault in the prison's yard at about 3pm. Staff at the prison scrambled to stop the assault but when police arrived they found one person seriously injured.
According to a 2013 report from NZME, Lee plead guilty in Rotorua to the aggravated robbery of two tourists.
A homicide investigation is now underway with a scene examination being completed on Friday. A post-mortem is now being carried out.
The other inmate, alleged to have attacked the prisoner, was placed into segregation at the prison.
"Corrections will carry out a full investigation and will ensure all evidence including CCTV footage is provided to police," said Chief Custodial Officer Neil Beales.