CHICAGO (AP) — Chicago police said late Friday they believe six family members found dead in their southwest side home were killed in a "targeted incident," though they're still trying to determine a possible motive.

It's possible someone in the family "was involved in something that could have targeted them," or that the killings occurred during a robbery or a domestic incident, police spokesman Anthony Guglielmi said.

Police found the six people — two children, two women and two men — dead on Thursday after one of the men's co-workers called 911 to report he hadn't shown up to work for two days.

Authorities initially said it was possible one person killed the other five before taking his or her own life. But the Cook County Medical Examiner's Office on Friday ruled their deaths homicides, saying five were stabbed to death and the sixth died of multiple gunshot wounds.

Police have added extra patrols as a precaution, though Guglielmi on Friday repeated earlier police statements that they don't believe the general public is in danger. There was no forced entry into the home and the house wasn't ransacked.

"This appears certainly centered and targeted on that family, and what we're trying to do is figure out why," he said.

Officers are exploring the backgrounds of the six victims, including talking to other family members and friends, Guglielmi said.

Authorities haven't released the identities of the victims, though the medical examiner's office described them as a middle-aged man and woman, an older man and woman, and two boys.

They said the middle-aged woman was shot to death, while the older woman and a middle-aged man suffered blunt trauma in addition to stab wounds.

The boys were 10 and 12.

Next-door neighbor Mayra Diego said Friday that the family members were quiet and peaceful people.

"That's what we're most sorry about," Diego said. "Because we could have done something, or being so close I feel like maybe we would have noticed something."

A relative said six people lived in the home — a couple, their son, their daughter and the daughter's two children.

"They were a normal family. Everything was fine," the relative, Noemi Martinez, 29, said from Dallas during a phone interview in Spanish. She said her husband was a nephew and cousin of the home's residents.

Martinez said the father worked at a factory in Chicago and the mother was a housewife. They were originally from the Mexican state of Guanajuato and had lived in Chicago for about a decade, Martinez said.

"Right now, we just want to know who did this. They didn't deserve this. We don't understand what happened," she said.

In the neighborhood, three teenage boys said they were worried about a classmate at Rachel Carson Elementary School who lived in the home. They feared he was among the dead.

"His favorite sport was soccer," Aaron Villazana said of his friend. Emmanuel Hernandez chimed in: "He'd get out of school and play soccer. ... He liked sharing."

"I just saw him three days ago. He was walking by. He told me, 'How are your basketball games going?'" said Jesus Anderade.

Earlier, Rosa De La Torre's 13-year-old son comforted her as she sat down and sobbed near the home, worried a friend could be among the victims.

Another neighbor, Lettie Magas, 68, lamented what she said has been an increase in crime in recent years.

"I feel safe as long as it's daylight out, but I won't come out at night, no way," Magas said.

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Associated Press writer Ivan Moreno reported from Springfield, Illinois.