Video: Robbers Caught On Tape

"They're putting guns in people's faces, threatening to shoot them. They've pistol-whipped somebody. [They are] very violent," said Det. Ed Troyer of the Pierce County Sheriff's Department.

Surveillance video from a robbery inside a Safeway store Thursday morning shows how the gang operates.

They enter the store in two groups. One team goes to the cash registers, the other sweeps the stores for customers or other employees.

They force an employee to go to each checkstand, looking for cash. At one point, an unsuspecting customer is threatened, forced to the ground, a gun held to his head while he give up his cash.

The robbers have hit grocery stores, video stores, convenience stores, mostly late and night and early in the morning.

Investigators are concerned because the robbers are so young and heavily armed.

The robbers have hit throughout Pierce County. The Violent Crimes Task Force, which includes the FBI, is working on the case.

There's a $4,000 reward for information that leads to an arrest.