A Billings man serving a life sentence at Montana State Prison for murder died Friday morning, prison officials said.
Cleveland Benjamin Boyer, 23, was pronounced dead at a local hospital in Deer Lodge at about 8:59 a.m. after prison staff found him in a cell.
"Inmate Boyer's death was unexpected and an autopsy will be performed by the state medical examiner," prison spokeswoman Linda Moodry said in a press release.
Moodry said a cellmate summoned the jail staff and said Boyer needed medical attention. It does not appear that foul play was involved, Moodry said, and there was no evidence that Boyer committed suicide.
A cause of death will not be known until after the autopsy, Moodry said.
Boyer was sentenced in January to life, plus 20 years, for the murder of his former best friend, Danny Valenzuela, at a downtown Billings convenience store.
Valenzuela was shot numerous times by Boyer with a .22-caliber handgun on March 13, 2011. He died six days later.
Boyer was convicted of deliberate homicide and felony tampering after a six-day trial in November 2012.