(HLNtv.com) -- The father of two Southern California children who went missing after their mother was killed pleaded Tuesday for their suspected abductor to release his daughter.
A massive manhunt is under way for James DiMaggio, whom law enforcement authorities describe as a friend of the mother, Christina Anderson.
The whereabouts of Anderson's children, Hannah, 16, and Ethan, 8, are unknown. Investigators believe they may be with DiMaggio, 40, the owner and sole resident of the burned home where Anderson's body was found, along with the unidentified remains of a child.
"Jim, I can't fathom what you were thinking. The damage is done. I'm begging you to let my daughter go. You've taken everything else," Brett Anderson, the children's father, told reporters.
"Hannah, we all love you very much. If you have a chance, you take it, you run. You'll be found," he said.
The father did not mention Ethan in his remarks, prompting a reporter to ask San Diego Sheriff's Department Lt. Glenn Giannantonio whether the child's remains might be those of the boy.
"We don't know who that is that was found in the rubble. It is a possibility that it's Ethan. It's a possibility that's another child that we haven't identified yet, or don't realize is missing yet," Giannantonio said.
"Right now, we just don't know, and we're praying that it wasn't Ethan," he said.
Authorities are following up on tips and casting a wide net for DiMaggio and the children.
"We've received some information that either Texas or Canada may have been the destination he was heading to. Realistically, we don't know where they're going," Giannantonio said. "We're looking everywhere."
Deputies and fire personnel were called to the scene of a residence and detached garage on fire in the enclave of Boulevard around 8 p.m. Sunday.
While extinguishing the fire, personnel discovered the body of Anderson, 42, of Lakeside, California. Authorities believe she was murdered.
They also recovered the remains of a child and the body of a dog.
Once California authorities issued the Amber Alert, information was distributed to residents' cell phones statewide through the Wireless Emergency Alert program, according to the California Highway Patrol.
The wireless program was instituted in December 2012, and this case is the first time is has been used statewide, CHP Public Information Officer Erin Komatsubara told HLN.
On HLN's "Raising America" on Tuesday, the children's aunt, Andrea Saincome, said that DiMaggio has known the family for years and that it would not have been unusual for the mother and children to be at his house.
"There was nothing out of the ordinary," Saincome told HLN's Christi Paul. "He seemed like a genuinely nice guy. He was close to the kids, and he was friends with my sister and my brother-in-law."
Police believe the children were last seen with their mother in Boulevard on Saturday. They were reported missing by their grandparents on Sunday. Giannantonio said he did not know what led them to believe their grandchildren were missing.
According to Giannantonio, DiMaggio and Anderson had "a close, platonic relationship."
Giannantonio would not release any details about how Anderson was killed, but said arson investigators believe they know how the fire was started.
Authorities also found burned weapons in the residence. Giannantonio did not disclose what those weapons were.
The Sheriff's Office released several photos of DiMaggio, and Giannantonio said he is believed to be driving a blue, four-door Nissan Versa with California license plate 6WCU986.
However, he might have switched vehicles, taken public transportation or could be hunkered down somewhere, Giannantonio said.
He asked for the public's help.
He warned anyone who sees DiMaggio and the children that he may be dangerous and they should not approach him or attempt to detain him. Instead, Giannantonio advised people to call 911.
Anyone with information about the case is asked to call the San Diego County Sheriff's Department Homicide Detail at 858-974-2321 or submit an anonymous tip to Crime Stoppers at 888-580-8477.
The FBI is assisting with the investigation.
"I'm hoping that the next time you hear from us will be maybe later on tonight with me announcing that we've located the children, they're fine, and Mr. DiMaggio is in custody," said Giannantonio.