The children treated him like an uncle. He was close friends with their parents.
James Lee DiMaggio is now a suspect in the death of Christina Anderson, the abduction of her 16-year-old daughter and the possible death or abduction of her 8-year old son.
Anderson's body was found in DiMaggio's burning home east of San Diego, near the dead body of a child who may be Ethan Anderson.
Brett Anderson, who flew from Tennessee to San Diego on Tuesday, pleaded with DiMaggio, 40, to release his daughter, Hannah, saying, "You've taken everything else."
"Jim, I can't fathom what you were thinking. The damage is done," he said outside San Diego County Sheriff's Department headquarters after being interviewed by investigators.
DiMaggio was wanted on suspicion of murder and arson in a search that began in Southern California and spread to Mexico and neighboring states. Authorities said he may be headed to Texas or Canada.
"Hannah, we all love you very much. If you have a chance, you take it. You run. You'll be found," Brett Anderson said, declining to take questions after reading a short statement.
On Sunday night, authorities found the body of Christina Anderson, 42, near a dead dog when they extinguished flames at DiMaggio's rural home. The child's body was found later as they sifted through rubble in Boulevard, a remote hamlet 65 miles east of San Diego on the U.S.-Mexico border.
Autopsy performed Tuesday
An autopsy on the child was performed Tuesday but no positive identification was made, said sheriff's Lt. Glenn Giannantonio.
"It is a possibility that it's Ethan," he said. "Right now we just don't know. And we're praying that it isn't Ethan."
Sheriff's investigators said Christina Anderson was close platonic friends with DiMaggio. The suspect was very close with Brett Anderson and like an uncle to his two children, Giannantonio said.
Christina Anderson's father, Christopher Saincome, said he had seen DiMaggio two or three times and described him as a good friend of his son-in-law.
Brett Anderson joined hundreds of family friends and neighbors at a candlelight vigil in the parking lot of El Capitan High School in Lakeside, an east San Diego suburb of 54,000 people, where Hannah was about to start her junior year. Pink paper cups stuffed between holes in the fence read, "Pray Hannah," and dozens of white, powder blue and pink balloons lifted into the air.
Hannah Anderson was a gymnast on her high school team who liked to dance and made friends easily.
"You would never see her without a smile on her face," said Marlee Friszell, 16, who attended Hannah's birthday party last week.
Ethan Anderson liked to play football and baseball and go fishing, said Cyrus Dawn, 17, a longtime neighbor.
Brett and Christina Anderson recently separated, Dawn said. Investigators called Brett Anderson her ex-husband, but he said they were still married.
An Amber Alert alerted freeway motorists, television viewers and cellphone subscribers to a blue Nissan Versa with California license plates that DiMaggio was believed to be driving. The FBI was participating in the investigation.
Monday marked the first time cellphone users were notified of a statewide Amber Alert in California through their phones. The alert system, which was introduced in December, sends messages automatically, based on the phone's location.
Associated Press news researcher Rhonda Shafner contributed to this report.