Police in a Dallas suburb dubbed the Christmas Capital of Texas searched for clues on Monday to explain the apparent murder-suicide rampage that left seven people shot dead among unwrapped holiday presents.

The dead -- four women and three men, one of them believed to be the gunman -- were found late Sunday morning in an apartment living room in the town of Grapevine by police answering a voiceless 911 emergency call, authorities said.

Two pistols were recovered from the home, said Sergeant Robert Eberling of the Grapevine police department, who called it a gruesome crime scene and the worst outburst of gun violence in the town's history.

Circumstances of the shooting remained sketchy, but Eberling said it appeared as though the bloodbath unfolded during a family holiday celebration as one man opened fire on six other people in the apartment, then killed himself.

No one was found alive by police arriving at the home, he said.

A community of about 46,000 people some 20 miles northwest of downtown Dallas, Grapevine is known for its wine-tasting salons and was recently proclaimed by the state Senate as the Christmas Capital of Texas for its abundance of annual holiday-season events.

This is obviously a terrible tragedy, Mayor William Tate said Sunday night in a statement given to Reuters. The fact that it happened on Christmas makes it even more tragic. This appears to be a family situation and anyone who has a family will be incredibly saddened by that happened.

VOICELESS 911 CALL

Police dispatched at about 11:30 a.m. local time on Sunday found the bodies in the first-floor living room of a two-story unit in the Lincoln Vineyards apartments, police said.

The 911 caller never spoke to police, and officers did not see the telephone when they arrived, officials said. Eberling said he believed police had to kick in the door to enter. No neighbours reported hearing gunshots, he said.

Eberling said the victims appeared to have just opened Christmas presents when the shooting started, and there was no visible sign of forced entry or a struggle.

By all appearances, they're all part of the same family, Eberling said. It's a gruesome crime scene to say the least, with that many victims in that (small an) area suffering gunshot wounds.

Two of the dead were believed to be in their 50s or 60s, while the others appeared to be young adults, ranging in age from about 18 to 20 years, according to police.

Authorities did not immediately identify the victims and did not speculate on a possible motive for the shooting.

The bodies remained in the apartment well past dark as investigators worked into the early hours of Monday morning processing the crime scene, police said.

Lincoln Vineyards is a middle-income complex near Colleyville Heritage High School, one of the area's most highly regarded schools.

Several neighbours told Reuters that children frequently played in front of the apartment, and they regularly saw young adults leaving for work.

Vanessa Barerra said the killings were especially disturbing in light of Grapevine's reputation as a safe place to live.

I did research and chose to live here because of the safety and the school district, she said. I'm glad my kids weren't here. They're with their dad.

(Additional reporting and writing by Steve Gorman and Karen Brooks; Editing by Tim Gaynor and Peter Bohan)