Police arrested 24-year-old Imran Ali Uddin, a registered sex offender at his home in Anaheim Tuesday.
The incident took place on Oct. 3 at a store located on the 2300 block of North Tustin Street in the city of Orange.
Investigators say Uddin approached the 13-year-old girl several times before exposing his private parts and fondling himself.
The girl was able to run to her grandmother. She later told authorities that the suspect also touched her inappropriately.
Uddin is being held without bail.