At least nine outlaw biker gang members were killed in Texas on Sunday when a brawl between rival groups erupted into a pitched gun battle in a parking lot.
Police told local reporters that they were amazed that none of the families eating in nearby restaurants were wounded in the crossfire as members of up to five gangs fought.
"In 34 years of law enforcement, this is the most violent crime scene I have ever been involved in. There is blood everywhere," Sergeant Patrick Swanton told the Waco Tribune.
"Twenty-five feet away there were families," he said. "This is one of the worst gun fights we've ever had in the city limits. They started shooting at our officers."
The battle broke at restaurant, part of the Twin Peaks chain of sports bars and a known biker watering hole, in a popular shopping and dining center in Waco known as the Central Texas Marketplace.
Police had been aware of a planned biker gathering in advance and officers intervened quickly, but not before gang members had escalated a punch-up to a knife and chain fight - and then to a shoot-out.
Authorities ordered businesses in the area closed and moved witnesses and suspects to safety, amid reports that more gang members were heading to the area to pursue the feud.
Stanton said police had made their concerns known to Twin Peaks, but that the bar - part of a chain known for its scantily clad waitresses - had not been cooperative.
Local news outlets reported that as many as 18 people were wounded, mostly from gunshot and stab wounds, and Swanton told reporters that more than 100 weapons were collected from the scene.
Local reports and television images showed scores of suspects being rounded up, questioned and in some cases loaded into police vans.
Waco police said in a Facebook posting that no officers were injured.
'Do not come to this area'
Initial reports said that the gangs concerned were the Bandidos and the Cossacks, but later police told local media that up to five distinct groups may have been involved.
So-called outlaw biker clubs sprang out of an American counterculture movement in the second half of the 20th century, and some now have global affiliations.
Recognizable by their leather jackets bearing gang insignia, at base the groups are clubs for like-minded individuals who share a love for motorcycles and a disrespect for authority.
But many group chapters - which elect their own leaders and have their own by-laws, symbols and initiation rules -- have become involved in organized crime.
In the United States they are particularly associated with gun-running and drug-trafficking and some outlaw biker clubs or their chapters have been formally designated as organized crime groups by the FBI.
News photographs of some of the Cossacks members taken in Waco after Sunday's violence also showed some of the mainly white gang members sporting neo-Nazi tattoos and symbols.
Local CBS television affiliate KWTX reported that the area was secured by police after the incident, and police warned residents to stay away as armed suspects continued to arrive.
"We are closing the entire Central Texas Marketplace if you are here leave now. For safety reasons we again assert do not come to this area!" Waco police said on Facebook.
"Officers are continuing to arrest individuals coming to the scene with weapons. This is not the time to sightsee as we are dealing with very dangerous individuals," it posted.
Waco is in central Texas and has a population of about 129,000.
The city is best known for a deadly confrontation in 1993 between the Federal Bureau of Investigation and heavily armed members of the Branch Davidian religious sect.
The 51-day standoff between the sect members and the FBI ended when the Davidians besieged compound caught fire, killing more than 80 people, including children.