The incident happened at the Twin Peaks Sports Bar and Grill in a shopping area called the Central Texas Market Place.
Eight people had died at the scene and a ninth died in hospital, police say. Several other people were injured.
One witness quoted by the Waco Tribune-Herald said the car park of the restaurant resembled “a war zone”.
Michelle Logan said: “There were maybe 30 guns being fired in the parking lot, maybe 100 rounds.”
Waco police said the shooting happened shortly after midday when two rival gangs got into a fight.
Police spokesman Sgt. W. Patrick Swanton said the fight started with punches and then involved knives and firearms.
He said there were concerns that groups involved in the shooting may have moved to other locations in and around Waco.
Sgt. W. Patrick Swanton asked residents to avoid the area until an all-clear is issued.
Waco police said no officers had been injured in the shooting.
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