A female adult left her 7-year old son alone inside her car while she ran an errand at the post office.  As she returned to the car, she saw the suspect  reach inside and snatch  her purse from her son who was holding on to it.  The suspect escaped with her purse with the help of an unknown female who drove him away from scene.  A composite sketch was later completed and broadcast on local news stations.  A half hour later, a citizen informant called the sheriff’s department to name the suspect.  A follow up investigation by sheriff’s detectives resulted in the arrest of both the male and female for strong armed robbery.