DALLAS - A gunman killed seven people at a home in a Dallas suburb on Sunday evening before being shot dead by police called to the scene, authorities said.The shooting took place in Plano, a suburb north of Dallas.David Tilley, a spokesman for the Plano Police Department, said the shooter was killed by the first responding officer after an exchange of gunfire. The officer was not injured.Seven people were found dead in the Plano home.Two additional shooting victims were taken to a local hospital. Their condition was unknown."We're trying to put all the puzzle pieces together," Tilley said.There was no information yet on the relationship between the suspect and the victims. Local media reports that the shooting occurred at a Dallas Cowboys viewing party could not be confirmed either.