A woman shopping at Marshall's in the Arsenal Mall left her wallet on the counter and, by the time she discovered it missing, someone had used her credit cards at shops in the mall.
The woman came back to Marchall's to report the missing wallet to store security, said Watertown Police Lt. Michael Lawn.
"(On security footage) store security observed the next person in line pick up the wallet," Lawn said. "The person used a credit card at a kiosk in the Arsenal Mall and made six more attempts to use it."
The person eventually returned the wallet to Marshall's, Lawn said.
Police continue to investigate the incident.