It happened on February 20 at around 6:30 p.m. at True Religion on M Street in Northwest.
The thieves were not wearing masks. The 12 people appeared to be just regular shoppers, but then they took over the store and stuffed items into shopping bags. Police say they made off with more than a thousand dollars in clothing.
Neighborhood Advisory Commissioner Ed Soloman says a group attempted to target the same store a second time days later.
"Twice it happened. Once they did get some merchandise, it happened real quick, 10 to 20 people come in the store," says Soloman. "Then we had another one where the police were nearby, they (the suspects) came in, then they left."
He says there have been several flash mob burglaries in Georgetown in recent years and encourages local business owners to sign up for DC Crime Alerts.
Crime Solvers is offering a reward of up to $1,000 to anyone who provides information that leads to the arrest and conviction of the person or persons responsible for the crime. You are asked to call police at (202) 727-9099 or text your tip to the Department's TEXT TIP LINE to 50411.