Folks looking to get their fright fix at a Bay Area Halloween event got more than they bargained for when a mob of teenagers barraged theme park visitors with a series of thefts and assaults.

The chaos erupted shortly before 11 p.m. Saturday when about 15 to 20 teens began snatching cellphones and other belongings from patrons at California’s Great America Halloween Haunt, which drew more than 20,000 people that night, said Santa Clara Police Lt. Dan Moreno. A few fights broke out, at least one of which stemmed from a theft.

Some who tried to escape the violence were left with bruises and scrapes, while at least one had a bloody nose. At least two people went to the hospital — a boy who was punched in the head and a girl who was shot with a stun gun. Both have been released, authorities said.

Police logged 15 theft and robbery reports, and four assault reports. One teenager was arrested on suspicion of robbery, while an adult was arrested on suspicion of public intoxication.

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