A masked robber held up the 99 Cents Only Store on Rohnert Park Expressway late Sunday night, taking an unknown amount of money, police said.

Police said employees called at about 10:30 p.m. and told them a woman, wearing a ski mask and hoodie, came into the store through the back storage area at about 10 p.m., which is closing time. She held two employees, one a store manager, at gunpoint and directed them to the store office, where she took some money. It was unclear Sunday night how much cash she took.

The suspect then ran out the back of the store and into a waiting vehicle, occupied by two or more armed people.

When police arrived, the employees were “shaken up” but otherwise OK, police said. They described the robber as an adult, either white or Latino, with no discernible accent.

The woman did not seem familiar to the employees. Violent Crimes Sgt. Jeff Justice said he’s not aware of any other robberies at the store.

Police are still investigating and have yet to identify any suspects.