Updated

Donny Hopkins was buying his wife cigarettes at a drug store when a man burst inside and screamed the unbelievable: A serial killer was savagely stabbing a man in the parking lot.

Hopkins, who knew a killer was stalking homeless men, bolted from the store to find a man repeatedly plunging a knife into a Vietnam veteran behind a Carl's Jr. restaurant.

"I'm yelling as loud as I can, 'Hey, stop!' at the top of my lungs. He just kept going and kept going," Hopkins told The Associated Press on Wednesday as he recounted the Jan. 13 attack.

Fumbling to dial 911 on his cellphone, Hopkins chased the suspect across the Anaheim strip mall and into a mobile home park, where police eventually collared a blood-covered suspect.

Hopkins, a 32-year-old forklift driver, was hailed a hero Wednesday and given a $5,000 reward for his role in the capture of Itzcoatl Ocampo, a former Marine.

"While we never encourage citizens to put themselves in danger, his actions saved unknown lives," said Tom Dominguez, president of The Association of Orange County Deputy Sheriffs, which paid the reward.

Ocampo, 23, an Iraq war veteran from Yorba Linda, has been charged with murdering four homeless men in Orange County over nearly a month. Police fanned out across the county better known as the home to Disneyland and multi-million dollar beachfront homes to urge the homeless to be careful and seek shelter indoors.

Hopkins, who lives with his wife, two children and mother in the trailer park where Ocampo was nabbed, received the check at a news conference outside the fast-food restaurant where 64-year-old victim John Berry is remembered with a collection of candles, flowers and teddy bears.

Hopkins, who had given money to Berry in the past, said he didn't feel like a hero because the man died.

"I did what I hope anybody would do if you see somebody in trouble," he said. "I'm just a guy who did the right thing. John was a Vietnam vet — he's a hero. That's a real hero."

Hopkins intends to use the reward to pay bills and help his mother, who lost her job a few weeks ago.

Prosecutors said Ocampo stalked each victim and stabbed them repeatedly with a knife sharp enough to cut through bone.

Authorities found a knife sharpener, a book titled "The Most Notorious Crimes in American History," dark clothes and a medical marijuana prescription letter in Ocampo's bedroom at his Yorba Linda home, according to court documents obtained by the Los Angeles Times.

Ocampo's father, who is homeless and lives in a disabled big-rig truck, said his son was troubled after he returned from Iraq in 2008. Refugio Ocampo said his son showed him a picture of one of the slain men and warned him to be careful just days before his arrest.

Prosecutors said Itzcoatl Ocampo targeted Berry after he appeared in a Los Angeles Times story about police warning the homeless about the serial killings.

The first victim in the killing spree was James Patrick McGillivray, 53, who was stabbed near a shopping center in Placentia on Dec. 20. The body of Lloyd Middaugh, 42, was found near a riverbed trail in Anaheim on Dec. 28. Paulus Smit, 57, was stabbed to death outside a Yorba Linda library Dec. 30.

Ocampo was being held without bail and is scheduled to be arraigned Feb. 17. Prosecutors have not announced whether they will seek the death penalty in the case.