Convicted serial murderer Ramon Escobar is suspected of killing his new cellmate on Friday at a central California prison, officials have said.
Escobar, 51, shared a jail room with Juan Villanueva at North Kern State Prison in Delano.
Villanueva, 53, was found unresponsive on 24 February at 8.49am.
The California Department of Corrections and Rehabilitation (CDCR) in a statement said that an officer approached the cell and “immediately summoned for medical response”.
Prison staff tried to save his life as an ambulance was called and Villanueva was taken to a treatment area.
Despite the attempts to resuscitate him, Villanueva was pronounced dead at 9.03am.
In the statement, officials have said that Villanueva was serving a life sentence with a chance of parole for the aggravated sexual assault of a child under the age of 14 in Los Angeles County.
Escobar is suspected of killing Villanueva and has now been placed in restricted housing pending an investigation, the CDCR agency said.
The Kern County coroner will determine the official cause of death, authorities said.
Other details have not yet been provided.
Serving a life sentence
Escobar, who is originally from El Salvador, was serving a life sentence without chance of parole after pleading guilty last year to killing five men and injuring seven others.
He also pleaded guilty to having killed his aunt and uncle in Houston, Texas.
Escobar fled Texas after killing his relatives in August 2018, prosecutors said.
Prosecutors added that Escobar was homeless when he began attacking people in Los Angeles and Santa Monica over the course of about two weeks in September 2018.
His trial was delayed until 2022 because of the pandemic.
Escobar arrived in prison custody last December and Villanueva arrived on 2 February, officials said.
Both Escobar and Villanueva were housed in the Reception Centre, which processes prisoners admitted from counties throughout California.