Authorities on Monday evening confirmed what Oregon City had feared -- that the body found Sunday in a barrel underneath a concrete slab behind Ward Francis Weaver III's house was that of missing 12-year-old Ashley Pond.

The body of 13-year-old Miranda Gaddis, a friend of both Ashley and Weaver's 13-year-old daughter, was found in a shed on the property Saturday and identified the following day.

Greg Horner, the chief deputy district attorney for Clackamas County, said he would present the case against the 39-year-old Weaver to a grand jury for an indictment.

"We expected this," said Tim Lyons, Weaver's attorney. "We are going to await the return of the indictment and see what the charges are and proceed from there."

Horner said it was too early to say whether he will seek the death penalty against Weaver, whose own father, Ward Francis Weaver Jr., sits on death row in California for having killed a young couple in 1982, raping the woman and burying her in his yard.

Weaver has been jailed since Aug. 13, when his son Francis called police to report that his father had raped the younger Weaver's 19-year-old girlfriend.

At the time, the son apparently told police that his father had killed and hidden Miranda and Ashley.

"I'm sorry that any of this even happened," Francis Weaver said Tuesday on ABC's Good Morning America. "I hope that now that [the girls' families] have closure and everything, they can go on with their lives and live their lives as good as they can."

He declined to give specifics on why he believes his father killed the girls, saying his father "needs to be brought to justice for what he's done" and public comment could hinder prosecutors' efforts.

Ashley, who would have turned 13 in March, was identified through dental records, said Gordon Huiras, the Oregon City police chief. He did not take questions.

The girls went missing last winter, prompting a nationwide search that ended over the weekend just a few hundred yards from the apartment complex where they had lived.

Authorities have said that they have moved as fast as they could to investigate Weaver, given constitutional limits on searches.

FBI spokeswoman Beth Anne Steele said search dogs were allowed in Weaver's back yard a few months ago, but it's possible that the bodies weren't there at the time.

Investigators returned to the property on Monday with high-tech equipment, a back-hoe, shovels and pickaxes to search for any evidence that might be hidden in the earth.

Steele said investigators didn't believe there were any more bodies on the property, but said investigators "do want to clear the property to make sure there's nothing else."

She refused to say how agents knew to look in the shed and beneath the slab for bodies.

"That's not something I'll comment on," Steele said.

Steele said investigators uncovered three more barrels but they contained only dirt. She also said investigators were nearly finished processing potential evidence inside the house.

The girls' relatives said Monday they were frustrated that the bodies were found so close to the girls' apartment complex.

"It makes a pit in your stomach. I get angry because she was right there the whole time," said Terri Duffey, Miranda's aunt.

"Detectives and police stood out here all hours with posters and they were right here all along," she said. "They came in and out of that driveway 100 times and they were right there, I mean right there and we couldn't do anything."

A chain-link fence erected by police around the property has become a makeshift memorial -- festooned with flowers, teddy bears, and notes in which people expressed their grief.

Throngs of mourners have been visiting the site, including some family members.

"We are never going to forget what happened. This is going to hurt my daughter for the rest of her life," said Wes Duffey, Miranda's grandfather.

"We know she's dead," he said. "We have an answer to that. The next question is, who done it."

Weaver weeks ago said he was a suspect in the FBI investigation, but denied any involvement.

Horner said Monday that Weaver had consented to the search that resulted in investigators finding the two bodies.

Last summer, Ashley had accused Weaver of molesting her, but he denied the allegations and was never charged. Family members and friends have said they had a close, and at times inappropriate, relationship.

Ashley's family last saw her on Jan. 9 eating breakfast with her younger sister before school. On March 8, Miranda disappeared from the same low-income apartment complex south of Portland.

The Associated Press contributed to this report.