(CNN) -- A man shot and killed eight people at a Dallas-area home where people had gathered to watch a Dallas Cowboys football game on TV, authorities say.
A police officer who was called to the home in Plano Sunday shot and killed the gunman there, authorities said.
The names of the victims and the gunman were not immediately released. The gunman had a connection to the house, Plano Police Chief Greg Rushin said, without elaborating.
"They (the victims) knew who he was. It wasn't a stranger-on-stranger crime," Rushin said at a news conference Monday.
The victims were men and women in their 20s and 30s, Rushin said.
"We've never had a shooting of this magnitude. We've never seen this many victims before. It's just a terrible event," the chief said.
Calls reporting multiple gunshots came in to Plano Police dispatch around 8 p.m. Sunday. An officer nearby approached the residence just two minutes later, where he heard gunfire and found shooting victims down in the backyard, Rushin said.
The officer "showed great bravery," immediately engaging and fatally shooting the armed suspect who was inside the residence, Rushin said.
Seven of the victims were pronounced dead at the scene, and two more were rushed to the hospital. One of the hospitalized patients later died.
The status of the surviving victim is unknown, Rushin said.
Multiple firearms of different types were recovered at the scene, the chief said.
The shooter may have been seen with a gun at a bar near the residence just before the shooting occurred, he added.
Police are not pursuing any other suspects, Rushin said.
The investigation is ongoing. Texas Rangers are handling the police-involved shooting investigation. The Plano Police Department is also conducting an internal administrative review of the officer, who has not been identified.