Frank Souza was already serving a life sentence at San Quentin for the murder of a homeless man in San Jose's Willow Glen neighborhood when he killed a fellow inmate who had killed a child.
The vigilante justice meted out in a San Quentin prison yard was meant to avenge a young girl's death, the killer said in court on Wednesday.
Frank Souza, 33, was already serving a lifetime prison term for murdering a homeless man when he stabbed Edward Schaefer to death in the summer of 2010 with a "makeshift metal spear," according to the Marin Independent Journal.
Schaefer had been in prison for less than two weeks, the beginning of a term he was sentenced to serve for killing 9-year old Melody Osheroff in a Novato crosswalk while drunk on his motorcycle, the newspaper reported.
Souza pleaded guilty to murder in order to avoid the death penalty. Souza, a member of the Aryan Brotherhood, will now serve a life sentence without possibility of parole, the newspaper reported.
In reading a statement in court on Wednesday, Souza said "the innocence of a child will be defended at all costs," the newspaper reported.
No one from the families of either Souza's victim, Schaefer, or Osheroff's family attended the courtroom to hear Souza speak.