GRAPEVINE, Texas -

Police in a quiet Fort Worth suburb worked yesterday to piece together a family history after a man dressed in a Santa Claus suit apparently shot six relatives and himself on Christmas.

Grapevine police spokesman Sgt. Robert Eberling said that the shooter showed up in the costume shortly before gunfire erupted, and that the family appeared to have been opening Christmas presents. Police responding to a 9-1-1 call found four females and three males dead. They also found two handguns.

"We think he was just inside there celebrating Christmas with the rest of them and decided for whatever reason that's how he's going to end things," Eberling said.

Investigators worked through Sunday night and into yesterday morning, searching the apartment where the bodies were found, along with vehicles parked outside. Police said they believe that the victims were related, though some were visiting and didn't live in the apartment.

Eberling said that investigators were assembling a "family history," and that the apartment was leased to a woman and her two children, one age 15 and the other either 19 or 20. He would not give other specifics.

"We're getting a clearer picture, but we're not ready to go on the record with anything until we find out from the medical examiner absolute confirmation of identities and the manner of death," Eberling said.

Autopsies of the shooter and the victims were being done yesterday by the Tarrant County medical examiner, but it would probably be today before their identities were released, he said.

Late Sunday evening, police intently searched a sport utility vehicle parked outside the apartment. The vehicle is registered to a man who listed his residence as a home two miles away, in the neighboring suburb of Colleyville.

Thomas Ehrlich, who lives near the home in Colleyville, said that he heard from neighbors that police went to the house Sunday. He said he believed that the man and woman who once lived there were estranged.