San Francisco police investigators returned Saturday to the Ingleside home near City College of San Francisco where five people were found dead the morning before.

Police Cmdr. Lyn Tomioka said the crime scene at 16 Howth St. contained too much information to process in a single day.

"It was a very violent homicide scene, as most homicide scenes are, but this was made more complicated by the number of victims," Tomioka said.

Investigators were still trying Saturday evening to determine what led to the multiple homicides, which were reported at 7:47 a.m. at 16 Howth St. in the city's Ingleside neighborhood.

Two police sources told KTVU Friday night that a San Francisco mass murder involving five victims appears to have been a targeted attack, possibly over money, and not a murder-suicide, as previously thought.

All of the residents were Asian and four of the five people found dead in a home near were related, police officials said.

Police told KTVU Friday the scene inside the Ingleside home was "very bloody" and among the worst they've seen.

There was bleach and paint all over the home, as if someone was trying to disturb the scene, police said.

A relative of the victims said the family who lived in the home were immigrants from China: a couple in their 60s, the couple's 32-year-old son and 37-year-old daughter, along with a woman in her 30s who was in a relationship with the son.

Property records indicated that the homeowner was 65-year-old father Hua Shun Lei.

Another daughter in her 40s, who did not live at the residence, entered the two-story home Friday morning and found three people dead, then called 911. Officers then arrived and found the three victims, and also found two others elsewhere in the home, police Cmdr. Lyn Tomioka said.

An investigator told KTVU no weapon was recovered from the home, and the injuries suffered by the five victims also appeared to indicate that it was not a murder-suicide.

Miriam Mendoza-Moody, a neighbor, said she heard yelling from inside the home.

"I did hear around midnight some very loud male-voice person arguing or yelling," she said. "It was discomforting, and my dog became agitated."

Mo Iranmenesh rents the home next door to the victims' and said the family owns the home he lives in. He said the 37-year-old daughter named Jess was always helpful.

"She's friendly," he said. "Every time I need help, she's there. Every time I lock myself out, she'd let me in."

Iranmenesh said he heard the other daughter screaming after she found the bodies Friday morning.

"It was a woman shouting, 'Can someone help me?'" said Iranmenesh.

Sources told KTVU there was no sign of forced entry, and investigators were looking at the possibility that the motive may have been a gambling debt.

"We have some information we're following up," said San Francisco Police Chief Greg Suhr. "But, I want to assure the public that we don't believe we have anybody at large that are looking to do random acts."

According to officials, the family moved into the home less than a year ago, and the father and son are in the construction business.

A police spokeswoman told KTVU autopsies would be conducted over the weekend to find out the cause of the deaths.

The case was believed to be isolated to the house and there is no threat to the public, Tomioka said.

"(Investigators) absolutely do not believe that this was a random act of violence," she said Saturday.

Howth Street between Ocean and Geneva avenues had been closed for much of Friday while police continued their investigation. Saturday, the house where the crime took place and two adjacent houses remained cordoned off by police tape.

San Francisco Police Chief Greg Suhr said in a phone interview Saturday that while they still hadn't recovered a murder weapon, they were following some good leads.

Police said they planned to return to the house Sunday.

Several bouquets of flowers laid on the sidewalk near the house since the shooting, one with a note reading, "R.I.P. Seff, you'll be missed."

Todd Sidebottom worked with Jess Lei, one of the family members who lived at the house and is presumed dead.

“I worked with Jess. She was an engineer at our company,” Sidebottom said. “(She’s a) real sweet person. One of the nicest people you'd ever want to meet.”

Mayor Ed Lee released a statement about the deaths Friday afternoon, calling them "a terrible tragedy."

"I extend, on behalf of the city, our support and sympathy to all family members and friends of the victims involved in this crime," he said.