Eyewitness News has learned Itzcoatl Ocampo asked for cleaning supplies and was given a bottle of Ajax by a deputy before he became ill.
"Typically, a powdery substance that can be utilized to clean their cell, they provide that to the inmates on a case-by-case basis when they request it to clean their cell. Typically the quantity that would be provided would be enough for one cleaning," said Lt. Jeff Hallock with the Orange County Sheriff's Department.
The incident raises serious questions about how well Orange County jail deputies were supervising Ocampo, who had mental health issues, his attorney Michael Molfetta said.
"If you spend three minutes with Ocampo, you are acutely aware of the fact that he has some mental issues. They were severe and they were obvious and they definitely were not contrived," Molfetta said. "With that being said, this was a guy who should have garnered the highest level of scrutiny ... and it wasn't done."
On Wednesday, guards found the 25-year-old shaking and vomiting.
The former Marine was transported from Central Jail to Western Medical Center where he was pronounced dead Thursday.
The murder suspect was being held without bail and awaiting his May 2014 trial date. He was suspected of killing four homeless men over a three-week period starting in December 2011. He was also charged with stabbing a mother and son to death in Orange County in 2011. Prosecutors were seeking the death penalty.
The 24-year-old served an eight-month deployment in Iraq in 2008 and was discharged in 2010. According to secret grand jury testimony, Ocampo reportedly joined the Marine Corps because "he needed to kill." Ocampo said he was disappointed when he did not see any combat during a tour of duty because he became a truck driver instead of a killer, court documents stated.
Ocampo's attorney is alleging negligence in his client's death.
The Orange County District Attorney's Office notified the victims' families via email.
Marie Middaugh says she is relieved she won't have to sit through a trial and hear the gruesome details of her son's murder. Lloyd Middaugh was one of the four homeless men stabbed to death.
Middaugh says she feels sorry for Ocampo's family, but now her loved ones finally have closure.
"We don't have to relive things again. I don't have to dread getting a phone call, we're going to have a hearing and all the horror coming back," said Middaugh.
The district attorney's office has launched a full investigation. An autopsy is scheduled for next week.
The Associated Press contributed to this report.