The Halloween advertisement for Great America, a huge amusement park in Santa Clara, California, not far from San Francisco, told park goers that “Fear is waiting for you."

It sure was.

As many as 100 marauding youths, some armed with Tasers, assaulted and robbed patrons, terrifying thousands of park goers, many of whom fled. The mayhem on Saturday, with about 20,000 people in the park, occurred during the 10th annual Halloween fest and broke out about 10:30 p.m., The Mercury News reported.

Park patrons reported encountering groups of robbers, some armed with Tasers, who ran through crowds stealing mobile phones, purses, and backpacks and sending visitors fleeing for exits. Some panicked visitors tried to scale park fences. About 30 patrons were injured, by one security guard’s estimate.

“It was terrible,” said a San Francisco mom who had brought her 17-year-old daughter and a friend to the haunt. “A kid in a hoodie ran up and pried the phone out of my hands.”

The mother, who does not want to be publicly identified because she was victimized, said she then frantically searched for her daughter amid terrified crowds as people were being assaulted. Her daughter and friend were not physically harmed.

“One lady got punched in the face,” she said. “Security did nothing to try to get those guys out.”

Police reportedly arrested one youth, Santa Clara Police Lieutenant Dan Moreno told the News. Visitors reported seeing other perpetrators escape into waiting cars.

The park had four city officers who were working privately, and as many as another dozen were called in to help, Moreno said. "Even so, police and park security were outnumbered, visitors reported," the News wrote.

Even the security supervisor reported being taunted and jumped by five assailants. "When the guard flipped one to the ground, he said, the others fled."