System of a Down's plans to launch its new album with a free outdoor show in Hollywood on Monday (9/3) went awry when local officials pulled the plug on the gig just before show time. A riot ensued, during which all of the band's stage equipment was vandalized or stolen.

An estimated 7,000 to 10,000 fans showed up for the concert, which was to be held in a parking lot (across from the club Vynyl) that was set up to accommodate about 3,500 people, according to the group's publicist. A number of fans who were denied entry charged past security and broke through barricades shortly before the group's scheduled 5 p.m. start, prompting officials to cancel the event due to crowd-control concerns.

System of a Down representatives tried to persuade officials to allow the band to perform several songs to appease the crowd, or to allow frontman Serj Tankian to go on stage to announce the cancellation, but both requests were denied, according to the group's publicist.

No announcement was made from the stage, and fans were never formally notified that the show was scratched.

Fans stood in the parking lot for more than an hour past the show's start scheduled starting time. As time passed, fans grew restless and began throwing shoes, water bottles, coins and trash on stage, and climbed into the backstage areas and the photo pit. Tensions increased as stagehands occasionally threw items back into the crowd. A movie crew shot footage from the stage, hyping the crowd and leading to speculation that the band would soon appear.

When security removed a black banner from the back of the stage that read, in white letters, "System of a Down," fans reacted by charging the stage, toppling speakers and both destroying and looting the band's gear. Tankian told the Los Angeles Times that the group lost all of its touring gear, including a drum set, guitars, basses and amplification equipment.

Rioters threw debris at police, smashed a number of car windows and building windows in the area and knocked over portable toilets.

The chaos lasted for about two hours and resulted in six arrests. Charges reportedly included offenses such as assault with a deadly weapon, felony vandalism and receiving stolen property.

Band manager David Benveniste told a local television station that the incident was ''absolutely, 100 percent avoidable," and said that, had officials let the band perform or at least speak to the crowd, "there was still a remedy, there was still a way to get out of that situation," according to a Reuters report.

Beneviste estimated the band's equipment losses at about $30,000, the report said.

Billed as a "thank you" concert for the L.A.-based band's fans, System of a Down's aborted concert was scheduled to precede the Tuesday (9/4) release of the group's sophomore album, "Toxicity" (Columbia). The group will kick off a tour later this month.

In the wake of the incident, the City of West Hollywood canceled System's Tuesday (9/4) in-store appearance at Tower Records on Sunset Boulevard.