Philadelphia police said they were able to prevent a "flash mob" on South Street Saturday night with the help of tipster parents.
The flash mobs usually start after postings on Facebook or Twitter. But this time, parents called police after seeing messages on their childrens' mobile devices telling them to come to South Street, officials said.
Police from other districts and members of the Narcotics Strike Force were sent to the area before 11 p.m. to help maintain order, but not before "the crowd brought traffic along South Street to a standstill and caused drivers to nervously sit in their cars while police tried to disperse the youths," Philly.com reported.
The chaos also caused several South Street businesses to lock their doors.
Police said shots were fired near 13th and South Streets at about 11:30 p.m., but there were no reports of injuries or major damage in the area, and by midnight, the area was back under control.
Three people were arrested Saturday night, including one adult, one teenager and one juvenile.
This is the third flash mob-type incident this year in Center City. Earlier this month, police arrested 28 people, most of whom are teens, and charged them with felony rioting. Their trials are scheduled for Monday, March 22 and Tuesday, March 23.