A shoot-out among rival motorcycle gangs at a popular Texas restaurant left nine bikers dead and 18 injured, and sent panicked patrons and bystanders fleeing for safety.
The violence erupted shortly after noon at a busy shopping centre about 90 minutes south of Dallas that draws a large lunchtime crowd.
Sgt W Patrick Swanton of Waco police said eight people died at the scene of the shooting at Twin Peaks restaurant and another person died in hospital.
The nine killed were all members of biker gangs, he said, as were the 18 people who were taken to hospitals with injuries that include stab and gunshot wounds. Some victims are being treated for both, he said.
"This is probably one of the most gruesome crime scenes I've ever seen in my 34 years of law enforcement," Sgt Swanton said, later adding, "I was amazed that we didn't have innocent civilians killed or injured."
Dozens of motorcycles were parked in a nearby car park. Sunday. Bodies were found in the car park of Twin Peaks and in another adjacent car park for a family restaurant.
Sgt Swanton said dozens of suspected gang members have been detained.
He said at least five rival gangs gathered at Twin Peaks for a meeting that he said focused on turf and recruitment, two areas where the groups have often clashed.
Preliminary findings indicate a dispute broke out in a toilet, escalated to include knives and firearms and eventually spilled into the restaurant car park.
There were 150 to 200 gang members inside the restaurant at the time. Shots were fired inside and outside the restaurant, the officer said.
Sgt Swanton described the interior of the restaurant, saying it was littered with bullet casings, knives, a club, bodies and pools of blood. The authorities would be working through the night to process the reams of evidence, he said.
Men in motorcycle jackets could be seen being taken away in police vehicles. Others sat on the ground waiting to speak with police.
Police were aware of the meeting in advance, Sgt Swanton said, and at least 12 Waco officers in addition to state troopers were outside the restaurant, part of a national chain that features scantily clad waitresses, when the fight began.
"We've been made aware in the past few months of rival biker gangs ... being here and causing issues," Sgt Swanton said.
Officers shot armed bikers, he said, adding that the actions of law enforcement prevented further deaths. It was not known if any of the nine dead were killed by police officers.
He said that the restaurant's operators were also aware of the meeting in advance, and he described the management as unco-operative with authorities in addressing concerns.
"Apparently the management (of Twin Peaks) wanted them here and so we didn't have any say-so on whether they could be here or not," he said.
A statement sent on behalf of Jay Patel, operating partner for the Waco franchise, said, "Our management team has had ongoing and positive communications with the police."
It added that the restaurant was co-operating with the investigation.
But Rick Van Warner, a spokesman for the Dallas-based corporate franchisor, said the company is reviewing the circumstances surrounding the shooting and is "seriously considering revoking" the Waco location's franchise agreement.
Three armed gang members were arrested later when they attempted to enter the shooting scene to retaliate against rival members, Sgt Swanton said.
He said the authorities are increasing security in the area to prevent further violence among the gangs.
He declined to identify the gangs, but many men wearing jackets inscribed with the words "Bandidos" or "Cossacks" were seen in the area.