Autopsies show six of the nine people found dead in Fresno, California, last week died of at least one gunshot.
The coroner's office says the other autopsies should be completed later today.
CBS News Correspondent John Blackstone reports seven of the victims are believed to be children of Marcus Wesson, 57, who is charged with nine counts of murder and is being held on $9 million bail.
Police say two of the victims may be children of incest - fathered by Wesson with two of his daughters.
Police are exploring motives.
Coroner Loralee Cervantes told The Fresno Bee that police were investigating whether Wesson had help in committing the killings, perhaps even by one of the victims.
She also said there was no sign the victims tried to struggle or escape.
The Fresno Bee reports the female victims are age 24, 17, 8, 7, and two 1-year-olds, and the male victims are age 7, 4 and 1.
The newspaper also reports that the 7-year-old boy was to have celebrated his 8th birthday on Sunday.
Wesson, walking out of the police station after many hours of questioning Saturday, reportedly turned to the horde of reporters and photographers and said: "I love you."
This is the largest mass killing ever in Fresno, a city of 440,000 people about 190 miles southeast of San Francisco, where shock continues to spread with each revelation.
Both the mayor and the police chief fought back tears as the bodies were carried out of the house.
"This is not Fresno," the mayor, "Heat of the Night" and "Grace Under Fire" actor Alan Autry, told the Los Angeles Times. "This is an aberration."
Sunday, two of Wesson's sons visited the crime scene that had been the family's home.
Instead of siblings and parents, the two instead found a makeshift memorial of cards, balloons, flowers, pictures and stuffed animals - left by a steady stream of visitors to the house.
"Anything can happen," said Serafino Wesson, who is 19 years old. "I don't know maybe he did, maybe he didn't, but he's such a good guy - I just can't believe he did it."
Ten years older, Dorian Wesson told the Los Angeles Times that the father he knows - who he hasn't seen in about a year - "was a good father. He wasn't abusive at all."
"I don't want to believe it," said Dorian. "I want to give him the benefit of the doubt. But they're all dead."
Identifying the victims and tracking down next of kin to be notified has been a difficult process.
"It's just very complicated," Deputy Fresno County Coroner Amy Hance said Sunday. "Who do you make notification to if eventually some of the victims are other victims' relatives?"
Wesson, 57, covered with blood but described by police as "very calm," was arrested Friday after a two-hour standoff at the family's house, where authorities found nine bodies tangled in a pile of clothing in a back room.
Officers cordoned off the home's perimeter again on Sunday and carried several boxes of material from the home.
Police Chief Jerry Dyer says no motive has yet been determined for the slayings, which were discovered as officers responded to a call from two of the women trying to get their children out of the house.
Police say Wesson had fathered children with at least four women, two of them his own daughters.
"We are exploring the possibility that there were other women he was involved with, either sexually or in some sort of polygamist relationship," says Dyer.
Officers were called to the house Friday for a child custody dispute. After finding the ghastly scene, some officers were placed on administrative leave and were being given counseling.
Police also found ten wooden coffins. Antique store owner Lois Dugovic said Wesson bought the hand-carved, mahogany coffins about five years ago, saying he planned to use the wood to repair a houseboat.
Frank Muna, an acquaintance, says Wesson at one point lived with several women - each of whom seemed to have a 'romantic' relationship with Wesson. Muna says he sold the group a house in 1999, where they lived until about eight months ago, when they moved because of complaints from the neighbors.
The Fresno Bee says they were upset because as Wesson renovated the house - he and the women were living in a tool shed with no sanitary facilities and at another point, in an old school bus parked at the property.
That same school bus is in the driveway at the scene of the killings. Inside it, according to the L.A. Times, are the colorful overnight bags of the children who are no longer there.
Detectives investigating the slayings believe they know the cause of death but are not ready to release that information.
"I can tell you that there were no mutilations," says the police chief, Jerry Dyer. "The bodies were intact."
Dyer adds that police "have not ruled out the involvement of any other suspects."