Nothing is known about Diego's life before or as the outbreak began. Diego was a former prisoner in Rikers Island in the Bronx. It is possible that he used to be a Mexican Gangster before the virus broke out and later got arrested. In the episode "Fallen Light" he is released from his cell along with his other cellmates. As everyone was about to exit the prison, Augustin Elizalde was conversing with a correctional officer hiding in his cell. Diego and another prisoner had design to kill him, due to the ill-treatment at the hands of the officer, before the prison was overrun. Augustin Elizalde then told them to leave him alone cause there were vampires still roaming the prison. Suddenly, the other prisoner shot the correctional officer in the arm and he fell down to the ground. As the officer was wounded, Diego finished him off by slashing him to death with a machete. Then the gratuitous sounds drew the attention of the vampires. One vampire correctional officer stung him in the back of the neck leaving him dead inside the prison.