Brett Anderson said that when he heard that a body was found in DiMaggio's burned-down house, he thought it was DiMaggio who had perished and was sad for him. "Things just downward spiraled from there," he said.
DiMaggio was the owner and sole resident of the burned home where Christina Anderson's body and the remains of the child were found.
One witness said that DiMaggio had a crush on Hannah, but evidence to corroborate that has not yet surfaced, Giannantonio said.
The remains of Anderson, of Lakeside, California, were found while firefighters extinguished a blaze that broke out at DiMaggio's home in the enclave of Boulevard around 8 p.m. Sunday.
Authorities believe she was killed. Her mother, Sara Britt, said Christina Anderson was 44 years old, not 42 as earlier reported.
Hannah Anderson was last seen at 3 p.m. Saturday at cheerleading practice, according to Britt and her other daughter, Jennifer Willis. Ethan was supposed to be at football practice at 8 a.m. Sunday but never showed, the two relatives said.
Ex-wife: Suspect didn't seem violent
DiMaggio's former wife, who was married to him for only six months, said he didn't show any violent tendencies during that period, but instead was a "nerdy" guy who showed a keen interest in video games, in particular, the game "Everquest."
"I would complain about the virtual reality game he would play all night. It was ridiculous. It was consuming him. It was addictive," the ex-wife, who wished to remain anonymous, told HLN's Nancy Grace.
"He is not a materialistic person, and he's very resourceful," she said.
The suspect's ex-wife added that she did not believe there was a romantic relationship between DiMaggio and the slain woman, describing their relationship as a "brother-sister type of deal."
California authorities also issued an Amber Alert. Once they did, 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 was the first time it had been used statewide, Highway Patrol public information officer Erin Komatsubara told HLN.
On HLN's "Raising America" on Tuesday, the children's aunt, Andrea Saincome, said that DiMaggio had 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."
Suspect linked to blue four-door car
The sheriff's office released several photos of DiMaggio, and Giannantonio said he was 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 be hunkered down somewhere, Giannantonio said.
He asked for the public's help, as did San Diego County Sheriff Bill Gore .
"We need all the eyes and ears out there we can get in trying to find both DiMaggio and hopefully those two kids," the sheriff said. "Citizens should not try to interfere with this person at all. He's already proven he's a pretty dangerous fella."
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.