Local officials see violent flash mobs as an emerging threat in the region. At Wednesday’s Metropolitan Washington Council of Governments board meeting, officials raised concerns about mobs like the group of teenagers that ransacked a Germantown 7-Eleven last month.

“We just cannot believe the brazenness that these young adults have shown,” said Metro Transit Police Deputy Chief Jeff Delinksi. The mobs are “very hard to predict and kind of hard to understand,” he said.