Two men, each convicted of multiple murders, sitting on death row in California's San Quentin State Prison, killed themselves just hours apart. One of the men was just sentenced to death last month.

California officials confirmed Monday that they found former US Marine Andrew Urdiales, 54, unresponsive during a security check at the nation's largest death row late Friday.

He was pronounced dead early by Saturday. Even more confounding, Urdiales was only sentenced to death on October 5.

He was convicted by an Orange County jury of killing five women in California, and previously faced the death penalty for three murders in Illinois.

Former US Marine Andrew Urdiales, 54 (left) was a former Marine, and a convicted of killing eight women- he was just sentenced to death in October- by Saturday he was dead from an apparent suicide. Also on Sunday, Virendra Govin, 51, was dead in his cell in an apparent suicide. Prison officials believe the two incidents are unrelated

Andrew Urdiales, an eight-time serial killer, glares back toward the media and gallery just prior to being sentenced to death on Friday, October 5, 2018

The brother of the second inmate who presumably killed himself, Virendra Govin (pictured) is also on death row for his role in the slayings of four business partners

The California victims were Robbin Brandley, 23, who was attacked as she walked to her car following a concert on Jan. 18, 1986, at Saddleback College in Mission Viejo; Maryann Wells, 31, on Sept. 25, 1988, in San Diego; Julie McGhee, 29, on July 17, 1988, in Cathedral City; Tammie Erwin, 20, on April 16, 1989, in Palm Springs; and Denise Maney, 32, on March 11, 1995, in Palm Springs.

The murders occurred while he was stationed at various U.S. Marine Corps facilities in Southern California.

He previously was convicted of killing Cassie Corum, 21, and Lori Uylaki, 25, both from Hammond, Illinois; and Lynn Huber, 22, of Chicago, in the mid-1990s and was sentenced to death there in 2004.

Former Illinois Gov. George Ryan commuted his sentence to life in prison in 2011 after capital punishment was outlawed in that state.

He had been on California's death row since October 12. While his cause of death is awaiting the results of an autopsy, officials said his death is being investigated as a suicide. He was alone in his cell in the 'adjustment center,' the first place condemned inmates are housed after arriving at death row.

Separately, authorities say they found Virendra Govin, 51, unresponsive alone in his cell in a different death row housing unit late Sunday. He was pronounced dead a short time later.

Govin was sentenced in December 2004 for committing four Los Angeles County murders, then setting the victims' family home on fire.

The victims were Gita Kumar, 42; Plara Kumar, 18: Tulsi Kumar, 16; and Sitaben Patel, 63. Govin, his brother Pravin Govin, and Carlos Amador, then set the Kumars' home on fire. Govin arrived on death row in January 2005.

His brother, Pravin, has been on death row since September 2005.

Officials said that while his death is also being investigated as a suicide, there is no indication that his and Urdiales' deaths are related.

California has not executed anyone since 2006 and inmates are far more likely to die from suicide or old age.

San Quentin is the largest death row in the US. Two inmates killed themselves within hours of each other over the weekend

Since 1978, when California reinstated capital punishment, 79 condemned inmates have died from natural causes, 25 have committed suicide, 13 have been executed in California, one was executed in Missouri, and one was executed in Virginia.

There currently are 740 offenders on California's death row.

While suicides are not uncommon, the pair of deaths comes weeks after a rare slaying.

Officials said Jonathan Fajardo, 30, was fatally stabbed October 5 in a recreational yard. Fellow inmate Luis Rodriguez, 34, is considered the suspect, but investigators were trying to determine a motive and how he obtained or was able to make the weapon.