A suspect was detained in San Francisco on Thursday in connection with a quadruple homicide investigation in Sacramento, police said.
Sacramento police tweeted just after 10 a.m. that four bodies had been found in a home in the 1100 block of 35th Avenue.
Police made the gruesome discovery in the Southland Park neighborhood, south of downtown, after a family member requested a welfare check at 7 a.m. Patrol officers got no response and made entry into the house, according to police spokeswoman Linda Matthew.
"This does not appear to be a random act," Matthew said. "We believe the victims were known to the suspect."
A suspect was taken into custody near Pierce Street and Golden Gate Avenue in San Francisco.
Police have not identified the victims or provided additional details about the ongoing investigation, including how long the victims had been left in the house before being found.
Sources told NBC Bay Area's sister station that the four victims were a mother, her two daughters and a niece. And a woman said she is the mother of the victim.
"I don’t know anything about what’s going on; it’s my daughter," said Anne Marie Smith. "I don’t know what’s going on. I’ll find out when I get down there."
Sources told NBC Bay Area's sister station KCRA in Sacramento that the man arrested in San Francisco is the woman’s estranged husband and the children’s father.
Investigators were processing the scene Thursday to collect forensic evidence. Officers are also canvassing the neighborhood looking for additional witnesses, Matthew said. Evidence technicians were expected to be at the scene through the night and into Friday morning because it such an extensive crime scene, Sacramento police said.
A 35-year resident of the south Sacramento neighborhood told KCRA that he had never seen such a large police presence in the area. Police believe the killings occurred around midnight Thursday.
"You don’t see stuff like this here," neighbor Luciano Fraga said.
San Francisco police could not immediately confirm the suspect's detention or identification.
Sacramento police have not provided details about how the victims died or a possible motive.
NBC Bay Area's Cheryl Hurd and Chuck Coppola contributed to this report.