SOLEDAD, Calif. (AP/CBS13) — Authorities said Saturday that they are investigating as a homicide the stabbing death of a 40-year-old inmate at Salinas Valley State Prison in Monterey County.

Isaac M. McCuan was pronounced dead at 12:17 p.m. Saturday in Soledad area prison, the California Department of Corrections and Rehabilitation said in a statement.

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McCuan’s cellmate, Juan Hernandez, 31, has been identified as the suspect. Hernandez came to the prison in 2013 to serve a sentence of life without parole for, among other convictions, first-degree murder and a street gang act in commission of a violent felony, the department said.

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McCuan was admitted to the prison in 2013 to serve a sentence of life with the possibility of parole, with a 35-year offense enhancement for a street gang act in commission of a violent felony.

Hernandez was re-housed in the Administrative Segregation Unit pending investigation, the department said.

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The prison has nearly 2,800 minimum- and maximum-custody inmates.