According to a Los Angeles Daily News report, Virendra (Victor) Govin, 51, was unresponsive at about 10:15 p.m. on Sunday while he was in custody at San Quentin State Prison in California.
Though CPR was administered, the inmate died several minutes later, authorities are investigating his death as a suicide.
Govin was sentenced for committing four murders in Los Angeles County in December 2004 including Gita Kumar, 42; Plara Kumar, 18: Tulsi Kumar, 16; and Sitaben Patel, 63, according to a CBS report.
He also set the Kumars’ house on fire in 2002.
Govin arrived on death row in January 2005 and his brother, Pravin, has been on death row since September 2005.
Authorities are also investigating another possible suicide of Andrew Urdiales, 54, a serial killer who was also found unresponsive during a security check at the same prison on Friday, according to a CBS report.
He was convicted of killing a total of eight people; five between 1986 and 1995 and three in the mid-1990s.
He had been on death row in California since October 12.
According to an NBC report, authorities do not believe that both deaths are related.