YORBA LINDA, Calif. – The father of the man suspected of killing homeless men in Southern California is himself homeless and says his son last week showed him a picture of one victim as a warning of the danger of being on the streets.

Refugio Ocampo, 49, also said Sunday that his son came back a changed man after serving with the Marines in Iraq, expressing disillusionment and becoming ever darker as he struggled to find his way as a civilian.

The father said he lost his job and home, and ended up living under a bridge before finding shelter in the cab of a broken-down tractor-trailer that he is helping repair.

His 23-year-old son, Itzcoatl Ocampo, was arrested Friday in connection with the serial killings of four homeless men since late December.

The first victim, James Patrick McGillivray, 53, was killed Dec. 20. The second victim, Lloyd Middaugh, 42, was slain Dec. 28, and the third, Paulus Cornelius Smit, 57, was killed Dec. 30.

The fourth victim, described by friends as a Vietnam War veteran in his 60s named John, was killed Friday. All four men were stabbed to death, police say.

Refugio Ocampo said that on Jan. 11, his son came to him with a picture of McGillivray. “This is what’s happening,” the father quoted his son as saying.

“He was very worried about me. I told him, ‘Don’t worry. I’m a survivor. Nothing will happen to me. I will find something. Count on it,’” the father said.

While Refugio Ocampo lives away from his family, they remain close. He saw his children every day, and his wife brings food to the parking lot where the truck is located in the city of Fullerton.

Itzcoatl Ocampo has been living with his mother, uncle and younger brother and sister in a humble rented house on a horse ranch surrounded by the sprawling suburbs of Yorba Linda.

Refugio Ocampo, who said he was educated as a lawyer in Mexico, immigrated with his wife and Itzcoatl in 1988 and became a U.S. citizen.

He described building a successful life in which he became a warehouse manager and bought a home in Yorba Linda. In the past few years, he lost his job, ran out of savings and lost his house.

His son entered the Marine Corps right out of high school in 2006 instead of going to college as his father had hoped. Itzcoatl Ocampo was discharged in 2010 and returned home to find his family in disarray, the father said.

Refugio Ocampo and his youngest son, Mixcoatl, 17, both described a physical condition that afflicted Itzcoatl in which his hands shook and he suffered headaches.

Medical treatments helped until he started drinking heavily, both said.

“He started drinking like crazy, too much, way too much,” the father said.

Both the father and a neighbor who is a Vietnam veteran tried to push Itzcoatl to get treatment at a veterans hospital, but he refused.

Refugio Ocampo said he wanted his son to get psychological treatment as well.

“He started talking about stuff that didn’t make any sense, that the end of the world was going to happen,” he said.

“Before, he had the initiative to do things, the desire. But after the military, he didn’t have any of that,” he said.

That was far from the son who in high school was a polite and motivated student, he said.

Refugio Ocampo said investigators came to him Friday night and showed him surveillance photos from a crime scene.

But he said he did not recognize his son as the person in the images.

“If he did it, it wasn’t right, obviously. But there’s something wrong with him,” he said.