A shootout among members of several rival motorcycle gangs on Sunday left at least nine bikers dead and 18 others injured in Waco, Texas, officials said.

The gunfire erupted about 12:15 p.m. outside a Twin Peaks Restaurant, and initially began as a brawl in which bikers were throwing punches and kicking one another, but soon after, the fight escalated.

Gang members pulled out chains, knives, clubs and firearms, according to the New York Times.

The chaotic, unexpected event frightened many shoppers and bystanders who were at the shopping plaza when bullets were fired.

"I was amazed that we didn't have innocent civilians killed or injured," said Sgt. Patrick Swanton, a Waco Police Department spokesman.

Waco police officers had anticipated problems when they witnessed hundreds of bikers from at least five groups gather at the shopping plaza, which was an alarming and intimidating sight.

"There were multiple people on the scene firing weapons at each other," Swanton said at a news conference. "They then turned on our officers. Our officers returned gunfire, wounding and possibly killing several."

Authorities said that they most likely saved a lot of lives by making sure officers were on the scene before the gunfire erupted, according to MSN.com.

"In 34 years of law enforcement, this is the worst crime scene - the most violent crime scene - that I have ever been involved in. There are dead people still there. There is blood everywhere," Swanton said.

The biker groups were not identified, but photographs of the members who were arrested showed a number of them in leather jackets bearing the names of at least three motorcycle clubs: Bandidos, Cossacks and Scimitars, the New York Times reported.

Swanton said authorities had received threats "throughout the night" from biker groups and were prepared Monday to deal with any more violence attached to Sunday's incident.

Originally, 192 people were arrested on charges of engaging in organized crime, but the number was reduced to 170 who were actually involved.