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GRAPEVINE, Texas -- Investigators believe that seven people who were found dead Christmas Day were cleaning up holiday wrapping paper when they were shot inside a suburban Fort Worth apartment, but a motive remains unclear.

All of the victims appeared to be related, and Grapevine police said they believe the shooter was among the dead. Investigators were meticulously searching the apartment, along with three vehicles parked outside, and didn't expect to finish until dawn on Monday.

"It appears they had just celebrated Christmas. They had opened their gifts," Grapevine Police Sgt. Robert Eberling said, adding that the apartment was decorated for the holiday, including a tree.

The four women and three men, aged 18 to 60, were found dead in an adjoining kitchen and living room area when police arrived midday Sunday, shortly after receiving a 911 call in which no one was on the other line, Eberling said. Two handguns were found near the bodies, he said.

None of the victims has been identified, but Eberling said it appears they all died of gunshot wounds. He said authorities still don't know what sparked the incident.

Grapevine Police Lt. Todd Dearing said investigators believe that the victims were related, though some were visiting and didn't live in the apartment. He said police are looking for other relatives to inform of the deaths.

"Seven people in one setting in Grapevine, that's never happened before. Ever," Dearing said.

Police and firefighters first rushed to the Lincoln Vineyards complex after receiving the open-ended 911 call at about 11:30 a.m., Eberling said.

"There was an open line. No one was saying anything," he explained.

So police went into the apartment, located in the middle-class neighborhood of Grapevine, not far from the upscale Fort Worth suburb of Colleyville. The apartment was at the back of the complex, overlooking the athletic fields of Colleyville Heritage High School.

But many of the nearby apartments are vacant, and police said no neighbors reported hearing anything on a quiet Christmas morning when many people were not around.

Jose Fernandez, a 35-year-old heavy equipment mechanic who moved to the complex with his family about six months ago, said he always felt safe in the area, but is now afraid to let his 10-year-old son play freely outside.

"This is really outrageous especially on Christmas," said Fernandez, who was visiting family for the holiday and returned to find several police cars parked outside his home.

"This has shocked everybody. It has scared everybody. I guess something like this can happen anywhere, but seven people dead. It's just very scary," he added.

Eberling agreed the area is fairly quiet, noting this would be the first homicide in Grapevine since 2010.

Christy Posch, a flight attendant who moved to the complex about six months ago so her son could attend the high school, said she lives a few buildings away and did not hear any gunshots.

"It's all families. That's why I moved here. No burglaries, no nothing," Posch said.

NBA Christmas schedule: What to watch in all five games

Back on Thanksgiving weekend, NBA commissioner David Stern and union head Billy Hunter met, with a noticeably increased sense of urgency on the league’s side. There was no question as to why—Stern wanted to push to reach a deal on a new collective-bargaining agreement so that the league could still air its prized package of games, on Christmas Day. The deal got done, and now comes the payoff.

“We got some incredible games on Christmas Day, I am excited,” Hall of Famer and ESPN analyst Magic Johnson said. “I am glad that the focus will be back on the game, back on the teams, back on the superstars we have in this league. I am ready to go. And they’re ready to go as well. And the fans are back and ready to go.”

In that case, let’s go. There are five games on tap, and each is worth a look. All times are Eastern.

Celtics at Knicks, noon

Worth watching: When last we saw the Knicks, they were being swept by the Celtics in a series that was deceptively close—the first two games were decided by a total of five points. The mantra then, though, was that after acquiring Carmelo Anthony and Chauncey Billups from Denver, the Knicks simply needed more time together to develop chemistry.

Instead, we got a lockout that slashed training camp down to two weeks and the Knicks roster went through a convulsion when they let Billups go and overpaid for Tyson Chandler. So, in what seems like an annual ritual, the Knicks will have to learn on the fly, and going against a Boston team that could return its starting five from the playoffs—Paul Pierce (ankle) may not play—will be a good first test of New York’s ability to do that.

Heat at Mavericks, 2:30 p.m.

Worth watching: There is very little reason that the Heat can’t step into this season firing on all cylinders. They’re (mostly) healthy, and they return pretty much everyone from their Finals team last year, with the addition of Shane Battier a big boost to the rotation. If you’re coach Erik Spoelstra, you’d like to see your guys—especially the star trio of Dwyane Wade, LeBron James and Chris Bosh—come out with a killer attitude and jump on the team that stopped their championship drive last year. A focused, no-nonsense effort would be a nice way to set the tone for the season in Miami.

It should help, too, that Dallas lost some key pieces, especially Chandler in the middle and J.J. Barea off the bench. Mavs coach Rick Carlisle will tinker with working new guys Lamar Odom and Vince Carter into the rotation.

Bulls at Lakers, 5 p.m.

Worth watching: It will be nice to watch Derrick Rose get started on his defense of his MVP award and his justification of his new contract, especially with new shooting guard Richard Hamilton aboard. But this game will mostly be about the Lakers, as new coach Mike Brown makes his debut, without Odom and with center Andrew Bynum out because of a suspension levied for a bonehead play in last year’s playoffs.

Brown also has to deal with Kobe Bryant’s thumb injury and Pau Gasol’s mindset, which could be an issue since he was nearly included in a trade for Chris Paul. It’s a new era for Lakers fans, and they might not like how things look at the outset.

Magic at Thunder, 8 p.m.

Worth watching: Like Stan Van Gundy doesn’t have enough to worry about, with a disjointed roster and a superstar big man who wants out of Orlando. Now, the league is adding insult to his injury by making his team play on Christmas, something Van Gundy has been vocal in complaining about in the past. Worse, the Magic have to travel to Oklahoma City, one of the tougher places to play in the NBA, against a team that is primed to take its spot as a championship contender this year.

Still, the Magic have the makings of a pretty good team, as long as Howard stays active and engaged while the trade rumors fly. Going up against Thunder center/agitator Kendrick Perkins should get Howard’s juices flowing—the last time he saw Perkins, he went for 28 points and 13 rebounds, while Perkins was scoreless in five shot attempts.

Clippers at Warriors, 10:30 p.m.

Worth watching: How many times has it been said that a Clippers-Warriors tilt is must-see TV? If this is the first time, it just goes to show how excitement has increased now that L.A. has added point guard Chris Paul to Blake Griffin’s team.

With Griffin and young center DeAndre Jordan, the Clippers have two of the three leading dunkers in the league from last year, and bringing in deft passers like Paul and Chauncey Billups has already earned the Clippers the nickname, “Lob City.” They will travel to the Bay Area to make their debut against the Warriors, a team that new coach Mark Jackson is hoping to instill with a new defensive mindset. Good luck with that, coach.