Two inmates serving life sentences have died after being attacked at California prisons, corrections officials said Wednesday.Robert Tunstall, 64, died Wednesday morning after another inmate attacked him in the recreation yard at Salinas Valley State Prison, according to a statement from the state Department of Corrections and Rehabilitation.Life-saving measures failed and Tunstall was pronounced dead about a half-hour after the attack, authorities said.An inmate-made weapon was recovered and a suspect identified as Lawrence Adams, 42.Tunstall was admitted to prison from Solano County in 1976, to serve life with the possibility of parole for first-degree murder, corrections officials said.Adams was admitted from Tuolomne County in 2007 to serve life in prison with the possibility of parole under third-strike convictions for arson and other charges. He also was serving additional years for two attacks on other inmates at separate prisons, authorities said.Meanwhile, authorities were investigating the death of an inmate at State Prison, Sacramento on Tuesday afternoon.Two fellow inmates assaulted Felipe Rodriguez in the prison yard and the 36-year-old was pronounced dead about a half-hour later.Two inmate-made weapons were recovered, authorities said.Rodriguez was serving life sentences, including one without the possibility of parole, for crimes including mayhem, extortion, attempted murder and kidnapping resulting in death. He was first sent to prison from San Bernardino County in 2015 to serve nine years for carjacking, authorities said.Investigators named two suspects: 41-year-old Selso E. Orozco Jr. and 36-year-old Mike A. Calderon.Orozco is serving a 23-year sentence on robbery and weapons charges. Calderon received a life-without-parole sentence after being convicted of first-degree murder.