Emmanuel Didas, 20, the other patient involved in the hospital's blunder had an unnecessary brain surgery carried out on him, although his complaint was in the knee. Didas is slowly recovering but remains partially paralyzed.
Meanwhile the government has apologized for the mix-up, which has been blamed on both men sharing the same first name.
Didas now cannot move his right side following the unnecessary operation.
Health Minister David Mwakyusa has announced the setting up of a commission to investigate the saga. He has pledged to send Mr. Didas to India for specialized treatment. Mgaya was also due to have treatment in India but expired before this was possible.
Mgaya had spent four days at the Muhimbili hospital's intensive care unit , but his condition got worse on Thursday. Despite being operated on, he died several hours later.
Meanwhile his family say they are not planning to sue the government - they always knew he only had a 50% chance of survival, as the tumor had grown so large.
Still they have urged the health ministry to employ qualified and compassionate medical staff.