A 57-year-old man surrendered to police after walking out of the house covered in what appeared to be blood.
The victims were seven children ranging in age from 1 to 8, a 20-year-old woman and a 17-year-old girl. All were thought to be the children of Marcus Wesson, whom police handcuffed following a brief standoff.
Authorities said Saturday that Wesson had been arrested on suspicion of killing the victims, but wouldn't comment until an afternoon news conference on what charges prosecutors might file.
It was a discovery so grisly that it made even veteran Police Chief Jerry Dyer weep.
"I've been with the Fresno Police Department for 25 years, and I've never experienced anything of this nature," said Dyer, who wiped tears from his eyes as officers carried bodies of the victims out of the home Friday night, cradling the youngest ones in their arms.
"We do believe at this time that the deceased individuals, most if not all, are the suspect's children," Dyer said. "This is obviously very unique and there may have been some type of ritual involved."
The victims' bodies were found stacked in a pile of clothes inside the single-story home. The coffins were stacked along a wall.
"Who knows? It could be a total coincidence," Dyer replied when asked why the coffins were there.
Officers had been called to the west-side neighborhood about 2 p.m. Friday by two women who said a man inside the house had their children and would not release them.
The man initially ignored orders to come out, running into a back bedroom as two women fled the house.
Police believe the suspect fathered the victims with the two women who called for help and the two who fled the home. Neither they nor the victims were identified, and Dyer declined to release the cause of death.
A neighbor, Chris Tognazzini, said he heard two gunshots moments before police arrived.
Dyer said the women who called authorities told them they had given custody of their children to Wesson two years ago and now wanted the youngsters back.
The slayings rocked Fresno, which Dyer said had seen only three murders during the previous 2½ months.
"The only thing we can do now is mourn. We mourn for the kids, we mourn for the police," said Mayor Alan Autry. "We will never be the same again."
The police chief said some of the first officers into the house had already begun counseling.
"They're going through a lot of emotional turmoil," he said, adding the officers were placed on administrative leave.
Six police chaplains remained on scene throughout the evening as homicide detectives continued to gather up evidence.
The house is located just a few blocks from railroad tracks, and the detectives' work was interrupted periodically by the sounds of passing trains.
Neighbors, who milled around outside, said they knew little about Wesson or the house where a large yellow bus was parked in the driveway Friday night.
"He never said 'Hi,"' said Linda Morales. "I'd drive by and he'd make a point to turn his face."
Another neighbor, Johnny Rios, said that on many nights he heard loud banging coming from the house, as though the people inside were building something.
"There was something up over there," Rios said. "I thought there was prostitution going on because there was always a bunch of women over there."