As the guns went off, Valentina instantly dropped to the floor, moving in a low crouch, still to the back door. Once out, however, she closed her eyes to concentrate. She wasn't overly efficient at her powers, not compared to others in her family, but she was creative. 

Through shear force of will, Valentina made the image of a deep black curtain over the door. To everyone, it would appear like they back of the building was in deep shadows, as if they were in a covered alley that didn't allow any light down. the illusion would be believable enough to anyone not familiar with the area, or not taking the time to think about it, and would give all those who made it out the door cover from gunfire.

with that, she continued to follow Belka, keeping an eye back to focus on the door to save as many as she could before she lost her concentration on the illusion.