Seven people (four women and three men) aged between 18 and 60 were found dead, late on Sunday morning, in the living room of a first-floor apartment in Grapevine, a suburb near the Dallas/Fort Worth International Airport, according to an Associated Press (AP) report.

The bodies were recovered shortly after Grapevine police responded to a voiceless 911 emergency call.

There was an open line. No one was saying anything, Grapevine Police Sgt. Robert Eberling said, adding, It was a gruesome crime scene to say the least, with that many victims in that area suffering gunshot wounds.

It appears they had just celebrated Christmas. They had opened their gifts, he added. The sergeant, quoted in the AP report, also said two handguns were recovered from the scene and it could be the shooter was among those dead.

The police have called this the worst case of gun-related violence in the town's history, according to a Reuters report.

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

Preliminary investigations have uncovered three vehicles, according to the AP report, parked outside the apartment.

None of the victims have been identified so far, although police believe them to be related to each other.