Police arrested a 56-year-old man who works for the state on Friday on suspicion that he killed two adults and two children in a quiet Northern California neighborhood.

Authorities did not release the names of the victims, but friends and relatives of a young family that lived in the Sacramento house feared the worst.

Rita Munoz, who lives in the neighborhood, said her grandchildren played with an 11-year-old boy and 14-year-old girl who lived with their mother in the house. Munoz said her neighbor’s mother arrived at the house shortly after the bodies were found Thursday and was heard crying “Oh my gosh, my only baby. My grandbabies are all gone,” after she learned what happened.

Later Munoz said she overheard the woman say- “I told her not to go back to him.”

Sacramento police declined to discuss the suspect’s relationship with the victims and said they haven’t determined a motive.

“It’s a horrible thing,” Ms. Munoz said.

Police originally detained Salvador Vasquez-Oliva in San Francisco about 145 km away on Thursday afternoon and formally arrested him on Friday morning.

The four victims were discovered on Thursday morning when police broke into the home after a relative reported that something might be wrong.

Vasquez-Oliva was quickly singled out by investigators on Thursday. Police said he is from Sacramento, but records show he is also is associated with an apartment near the University of San Francisco, six blocks from where police found him. The building is in a nice neighborhood, but is worn and run down. There was no answer at the door, though a light remained on inside.

The California Employment Development Department, which administers the state’s unemployment checks, said it has employed Vasquez-Oliva as an office technician since 2014.

The single-story beige home with sculpted shrubbery where the bodies were found has a basketball hoop in a driveway that police blocked with yellow crime scene tape. It’s located in a tree-lined residential neighborhood of neatly maintained homes near a church.

Police have not said when or how the victims were killed.