Three men and four women were found in the Grapevine, Texas, home shortly before 11:30 a.m., according to local police. Two handguns were found in the apartment.
All of the victims were believed to be family members ages 18 to 60, according to police.
"We are pretty confident that the shooter is among the deceased victims inside the apartment. We are not actively looking for a shooter that we believe is at large," said Grapevine Police Sgt. Robert Eberling.
Police said it looked like everyone had just opened their Christmas gifts and were cleaning up the wrapping paper when the shooting took place.
Police and firefighters rushed to the scene after receiving an 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 entered the apartment.
The Associated Press contributed to this report.