The four suspects were taken into custody on Tuesday afternoon without incident at the Silverton Hotel and Casino.
The suspects are identified as Ka Pasasouk, 31, of Los Angeles; Howard Alcantara, 30, of Glendale; Donna Rabulan, 30, of Los Angeles; and Christina Neal, 33, of Los Angeles.
Pasasouk was arrested on suspicion of murder. The three others faced charges of aiding a felon; Alcantara faced an additional charge of robbery.
Court records show Pasasouk has an extensive criminal record and was on probation at the time of the killings. He has several convictions dating back to at least 2004.
All four suspects remained in Clark County jail and were expected to be extradited to Los Angeles in the coming days.
The shooting happened around 4:30 a.m. Sunday outside a home in the 17400 block of Devonshire Street.
On Tuesday, LAPD Chief Charlie Beck refused to give details about what may have led to the quadruple murder, in the interest of protecting the investigation.
But law enforcement sources told the Los Angeles Times that the killings appeared to stem from a dispute over personal property, although they wouldn’t say what kind of property.
The sources, who spoke on the condition of anonymity because the case was ongoing, said detectives were surprised that the dispute would have led to multiple deaths.
One of the suspects was believed to have lived at the Northridge home, which authorities said had been converted into an illegal boardinghouse. It’s unclear whether any of the victims lived there.
Authorities have not released the victims’ names. Police said the women were in their mid-20s; one man was in his mid-30s and the other man in his late 40s.
Family members told KTLA that one of the female victims was 25-year-old Amanda Ghossein.
They said Ghossein has a 1-year-old daughter and was about to celebrate her 25th birthday on Tuesday. She had dreams of becoming a fashion designer.
“I don’t understand who can do this, who can just kill someone not knowing if they had a family or not,” said tearful sister Alyssa Verrigni.
Rolina Calabia told KTLA that her brother, Robert, of Eagle Rock, was also among the victims.
“They killed him execution style. Who would do such a thing?” she wondered. “Why would you execute someone? You’re not God.”
According to new reports, three of the victims — a man and two women — were shot on a walkway on the left side of the home.
They were wearing hooded sweatshirts and were about two feet apart, a source familiar with the case told the Times. All three had at least one bullet wound to the head.
Two of the victims were found face down. One victim was crumpled on her knees with her face buried in her hands, as if she had been praying.
The fourth victim — a man — was farther away and appeared as if he was trying to run to the backyard when he was shot. He had at least one gunshot wound, the source said.
Authorities said that up to 17 people lived at the home, with conditions that Englander described as “deplorable.”
City inspectors red-tagged parts of the property Tuesday after finding “numerous code violations,” said Department of Building and Safety spokesman David Lara.
The owner of the home, Yag Kapil, said he rented out rooms but denied he was running a boardinghouse.
Kapil, 78, who lives at the home, said he was bedridden and was asleep at the time of the shootings. He said he didn’t hear anything and didn’t know the victims.