JACKSONVILLE, Fla -

The mother of a 20-year-old woman who was shot and killed Saturday night while working at a MetroPCS store on Main Street is pleading for someone to help find her daughter's killer.

"I just want him off the streets," said Darlene Farah, the mother of Shelby Farah. "He's on the streets. I don't want him to kill nobody else."

Detectives said the man, seen in surveillance video, walked into the Northside store and robbed Shelby Farah, then killed her.

Farah was a college student, a family girl and a mentor.

Shelby Farah

"This is the Shelby that everybody knew right here: always smiling, always laughing, always jolly," Darlene said while showing a picture of her daughter.

"I had about 18-20 girls that looked up to her," said Bryan Jones, of Communities In Schools.

Jones said until Farah took the job at the cellphone shop, she worked as an after-school cheerleading coach for young girls. She taught much more than the sport. She taught them life lessons.

"The children loved her, the staff loved her, and everybody around the school that met her loved her," Jones said.

Police say this isn't the first time a MetroPCS retailer has been robbed recently. At least four others around town were hit in the last year. One of those robberies, though not related, was at the same store in January. Only one ended with an arrest.

"These type of businesses need to find a better way to handle cash transactions," said Channel 4 crime and safety analyst Ken Jefferson.

He said stores like MetroPCS have become seemingly easy targets for criminals, and something needs to be done to increase security.

"Criminals know that there's a lot of traffic coming in and out," Jefferson said. "Most of the traffic coming in is people making payments to cellphone services, so they deal with a lot of cash."

The owner of the store is in Tallahassee and was unavailable to comment on the safety precautions he's going to take in the future after this tragedy. The company's corporate office released this statement:

"We are shocked and saddened by this senseless act of violence at one of the independently-owned dealer stores. Our sympathy is with colleagues, friends and family affected by this tragedy. The safety of our employees is of the utmost importance and that is why we are working closely with law enforcement on the investigation."

There is no word yet on funeral plans for Farah.

Anyone who has any information about the identity or location of the man seen in surveillance photos is asked to call the Jacksonville Sheriff's Office at 904-630-0500 or Crime Stoppers at 866-845-TIPS.