FONTANA (AP) -- A 16-year-old boy entered the Southern California home where his mother lives with her husband and two younger children. After being unable to reach her all day, he was worried something was wrong. He was all too right.

In a house where blood covered several rooms, he found all four family members dead from gunshot wounds, police said Tuesday.

Fontana police concluded it was most likely a murder-suicide.

Ramon Miranda, 38, apparently shot and killed 34-year-old Silvia Miranda and their children, 12-year-old Ramon Jr. and 10-year-old Rayna, before turning the gun on himself, according to police and the San Bernardino County coroner's office.

The woman and the children had been shot several times and the man was shot once in the head, police spokeswoman Martha Guzman-Hurtado said.

Investigators found a handgun.

"Everything that has been confirmed so far indicates it could be a murder-suicide, but that has not been confirmed," Guzman-Hurtado said. "They are questioning other people before making that conclusion."

However, investigators weren't looking for any suspects, she said

Guzman-Hurtado said records show the last time police visited the home was in June 2010 for an unspecified code-enforcement matter.