Updated

Southern California authorities have identified four family members who were shot to death in a murder-suicide at a Mission Viejo home.

An Orange County Sheriff's Department statement Thursday says 21-year-old Michael Sheer used a shotgun to kill his father, 55-year-old Mark Harrison Sheer; his mother, 54-year-old Lydia Ann Sheer, and his 15-year-old sister, Amy Joanne Sheer.

Deputies went to an area near Pacific Hills Road on Monday after reports that a man was yelling and shots may have been fired.

However, authorities say they found nothing.

A relative found the bodies of the family on Tuesday.

Investigators are still trying to determine a motive for the killings.

Mission Viejo is a city of about 95,000 about 50 miles southeast of Los Angeles.