SAN CLEMENTE -- Sheriff's officials say five family members found dead and decomposing in an upscale San Clemente home were all dressed in black clothing.
The bodies - three generations of the same Turkish-American family - were found last Sunday when two brothers broke into the house after not hearing from them for some time.
Investigators believe the bodies went undiscovered for two to three weeks.
Authorities said the two parents, Manas and Margrit Ucar, were found on the floor near a closet, Lt. Erin Giudice, spokeswoman for the Orange County sheriff.
Two guns were found near their bodies and both had gunshot wounds. One of the guns was found to be registered to Margrit Ucar and investigators are still looking for records on the second gun, Guidice said.
The Ucar's two twin daughters, Margo and Grace Ucar, both 21, were found lying in a bed in the bedroom, Guidice said, although she would not specify if they were laying on the same or separate beds.
Margrit Ucar's mother, Fransuhi Kesisoglu, 72, was sitting in a chaise lounge in the room.
The bodies were discovered on what would have been Margrit Ucar's 49th birthday.
Authorities have not ruled out homicide or suicide and are awaiting autopsy results and toxicology tests before announcing the cause of death.
Autopsies are still incomplete, and because the bodies were so badly decomposed it could take up to eight weeks to complete toxicology tests, Giudice said.
When asked whether investigators are looking into the possibility the deaths could have been planned together by the family, Giudice replied: "We are certainly looking into all aspects and all possibilities.
That's why we want to be really careful when we talk about murder-suicide."
Deputies had visited the home overlooking the Pacific twice in the past two weeks, prompted by calls from a concerned neighbor and worried relatives.
But deputies found nothing suspicious, and the callers conceded the family may have taken a vacation.
On Sunday, two brothers forced their way into the house, only to discover the bodies.
Because the house was built into a cliff, the bedroom suite where the bodies were found was below ground level, shielded from view and well-insulated, Giudice said.
"Everything was closed up," she said. "The family and the neighborhood thought they were on vacation."
Margo and Grace Ucar both finished work toward bachelor degrees in biology at the University of California, San Diego, this past winter, said Pat Jacoby, a spokeswoman for the university.
Manas Ucar came to the United States in the 1970s and was on the Syracuse University faculty about five years, said Eugene Drucker, a retired Syracuse professor who supervised Manas Ucar's doctoral dissertation in mechanical engineering.
Ucar's wife, Margrit, also immigrated from Turkey and received her U.S. citizenship in 1987 while in Syracuse, according to an article in the newspaper The Post-Standard.
Manas Ucar became a consulting engineer after leaving the university, then moved to California in the mid-1990s, Drucker said.
The Web site law.com lists Ucar as an expert on accident reconstruction, specializing in fires, explosions and seat belt use.
The family's home is in Sea Pointe Estates, a small, gated community in San Clemente, about 65 miles southeast of Los Angeles at the southern edge of Orange County.