Moments after shooting Renee Farrow in the head and back during a Father's Day family celebration in Overbrook, Marvin "Brown" Nesmith ran downstairs after Rafeea Parker, Farrow's son told the Daily News yesterday.

He chased her around a parked truck, then to the lawn. She knelt, pleading for her life. But he shot her in the head anyway, said the son, Eric Farrow.

Nesmith, a troubled man with a criminal past, had been Farrow's boyfriend for almost a decade. A mental-health worker, she had stayed with him because she believed she could help him, Eric said.

On Sunday, Nesmith waited until Eric and two of his cousins had gone to buy food for a Father's Day dinner. Then, with at least six relatives inside the house, police said, he killed Renee Tanya Farrow, 55, and Parker, 31, who had been dating another of Farrow's sons.

" 'Brown shot my mom dead!' " yelled Kyfee Kessler, 8, according to Eric Farrow, 38, who recounted his relatives' version of the tragic details in an interview yesterday outside the house.

After the shootings Nesmith ran off but soon returned, allegedly trying to break a window in the front door and demanding entry. But he couldn't get in. Relatives found Renee upstairs, gasping for air.

Responding to a report of a domestic disturbance, police later arrested Nesmith, 56. He was charged with two counts of murder. Neither the police nor relatives of the victims could think of a motive.

"It's a really tragic situation," said neighbor William Hutchings.

Even before Sunday, Nesmith had shown erratic behavior. "He was fussing - always ranting and raging," said Cynthia Ragin, 36, mother of Eric Farrow's children.

On Sunday, in fact, he hadn't seemed any more agitated or argumentative than usual, Ragin said. But Eric Farrow believes that he was high.

"I can't remember him sober, even when I was young," said Farrow. He was 5 when he met Nesmith, who didn't start dating Eric's mother until Eric was in his mid-20s.

"He wasn't one of those stable men," Farrow said.

Renee Farrow was employed at COMHAR Inc., a nonprofit mental-health facility in North Philadelphia, her son said.

"My mom has to help needy people," Farrow said.

Renee Farrow had stayed with Nesmith for nine years in spite of his struggles, her son said. They had moved into the two-story rowhouse in September.

"She didn't want to leave him, because she thought that she could make him better," said Farrow. "She always thought she could fix people."

Farrow's family hadn't thought so. " 'This is who you choose to be with,' " Farrow said he had told his mother after warning her about Nesmith.

He had hoped he could convince her to leave Nesmith, who since at least 1971 has faced charges ranging from simple and aggravated assault to possessing instruments of crime to burglary and larceny.

" 'I don't care [if] your son is here - I'll do the same thing I did to you last night,' " Eric once heard Nesmith say to his mother, he said.

Eric, a solidly built man who works as a porter and is taking classes in behavioral health at Community College of Philadelphia, said he had to resist pummeling Nesmith then.

Parker, Farrow's brother's girlfriend, was a "strong, no-nonsense woman," said Ragin. "Nesmith probably shot her out of fear."

When Eric Farrow did some time in prison, he said, his mother cared for some of his children until he got out and resumed his responsibilities as a father.

"She was the glue that held my family together," he said.