Los Angeles (CNN) -- A California grand jury indicted a 23-year-old former Marine Thursday on charges of killing a mother, a son and four homeless men, prosecutors said.
Itzcoatl Ocampo faces six counts of murder with special circumstances for the stabbings, which the Orange County District Attorney's Office described as "a serial thrill-kill spree."
He is being held without bail and is scheduled to be arraigned on the indictment Tuesday, prosecutors said in a statement.
Ocampo served in the Marines from July 2006 until July 2010 and was deployed to Iraq for six months in 2008, according to Marine service records. He completed his service, with the rank of corporal, with the 1st Marine Logistics Group at Camp Pendleton, south of Orange County.
Ocampo's arrest last month left those who know him confused.
The suspect's father, Refugio Ocampo, who is himself homeless, told the Orange County Register it was hard to believe his son could be involved in the killings.
"I saw him so many times giving the last money he had in his pocket ... to the homeless, to the people that (are) asking for some help. ... My son's always been a role model," Refugio Ocampo said in a video interview posted on the newspaper's website.