They had just finished opening presents on Christmas Day, police said, but a short while later all seven were dead. It appeared they were in the midst of cleaning up the wrapping paper.

The shooting in Grapevine, Texas, a Dallas suburb, left neighbors in shock and horror as they biggest holiday of the year revealed a gruesome and bloody murder. Investigators said the motive was unclear as to why seven were left dead inside the apartment on Christmas Day.

The victims, who were not identified as police worked into early morning hours the day after Christmas to solve the crime, appeared to be all related. They included four women and three men, ages 18 to 50. Grapevine police said they think the shooter was one of the dead found at the apartment -- apparently a classic murder-suicide.

It appears they had just celebrated Christmas. They had opened their gifts, said Grapevine Police Sgt. Robert Eberling, according to The Associated Press.

Eberling said the apartment was decorated for the holidays, including a tree.

All of the seven victims appeared to have died from gunshot wounds. Early in the morning on Dec. 26, police were searching for family of those who didn't live in the apartment to tell them of the horrible news.

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

He said police received a 911 call at 11:30 a.m. on Christmas Day.

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

Police and firefighters responded to the call from the Lincoln Vineyards  apartment complex, which overlooks athletic fields for Colleyville Heritage High School. Inside, they found the Christmas massacre.

Two handguns were found in the apartment, police said. One official called the gruesome crime scene the worst massacre in Grapevine's history.

This is obviously a terrible tragedy, Mayor William Tate said in a statement 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 what happened.