Relatives were celebrating a child's birthday Saturday night at a skating rink when a gunman opened fire in an apparent domestic dispute, fatally shooting five attendees before killing himself and wounding four others, police said.

The man started arguing with a woman in Forum Roller World's front area where the party was being held, although the rink was not open to the public because the family had rented it for several hours for the private party, Grand Prairie police spokesman John Brimmer said.

He said investigators were still trying to determine how many people were inside the building in Grand Prairie, about 20 miles west of Dallas, when the shootings happened about 7 p.m.

Authorities did not immediately release the victims' names or ages or say how the gunman may have been related to those who died. Brimmer said no young children or rink employees were killed.

The injured were taken to hospitals, and their conditions weren't immediately disclosed. Grief counselors were available for witnesses, victims and family members, Police Chief Steve Dye said.

Derrian Harris, 18, of Grand Prairie said he rushed to the rink Saturday night after hearing about the shootings. He said he usually goes there every Friday night and was worried about whether any of his friends were hurt, but later believed that he didn't know any of the victims. He said he has never seen so much as a fight at the rink.

"All kinds of people come here to skate, and everybody gets along," Harris said.

Some people who were at nearby businesses when the shootings happened described seeing adults and children in a state of panic rushing out of the rink, some wearing roller skates.

"They just looked terrified," Cody Poston, a witness, told WFAA-TV. "There's several people crying. The kids were just kind of oblivious."

Great Southwest Parkway, a major street in an industrial area in front of the rink, was partially blocked off after the shooting. About a dozen police vehicles with lights flashing and a few fire trucks were parked nearby, with a mobile command station in front of the building. As of midnight, investigators continued walking in and out of the building and bodies were still inside.

Byron Raspberry of Grand Prairie said his children go to the rink frequently because it is near their home.

"It doesn't make any sense," Raspberry said. "I don't feel safe at all."