An Iraq war veteran has been charged with stabbing four homeless people to death in southern California - and police say he planned more attacks.
Itzcoatl Ocampo, a 23-year-old former Marine whose own father is homeless, allegedly stalked the victims, stabbing some of them more than 40 times.
He has been charged with serial murder and using a deadly weapon.
After the killings began in December, police undertook night patrols and urged homeless people to seek shelter.
Mr Ocampo was arrested last Friday when bystanders gave chase after he allegedly stabbed a 64-year-old homeless man to death outside a fast-food restaurant in Anaheim, California.
'Relished media attention'
Orange County District Attorney Tony Rackauckas told a news conference on Tuesday in Santa Ana city that there was no indication the accused was mentally ill.
"It will be proven that the defendant planned all of his murders in advance; that he stalked his victims; that he looked for the right opportunity to execute them," he said.
Mr Ocampo had "relished the media attention of the crime", the district attorney added.
He also said the accused "had selected others" to attack, although the district attorney gave no further details.
Mr Ocampo had picked the final victim, John Berry, because he had appeared in a news article in which police warned homeless men to be careful, Mr Rackauckas said.
Police have said Berry filed a report to the authorities that someone had been following him, but they had been pursuing too many leads to investigate it.
What could have prompted the killings is not clear. According to the Los Angeles Times, Mr Ocampo's friends remember him giving money to the homeless.
He is being held under 24-hour surveillance in isolation at a jail in Orange County.
The district attorney has appointed a panel to decide whether to push for the death penalty.
The accused's family say he was a troubled man after returning from the war.
He came home in 2010 after being discharged from the military. But his parents separated and one of his friends was killed during combat in Afghanistan.
Days before his arrest, Mr Ocampo visited his father, who had ended up living under a bridge after losing his job.
His said his son had warned him about staying on the streets, and showed him a picture of one of the stabbing victims.
"He was very worried about me," his father said.