Police say four women got into an argument around 9:30 p.m. Thursday at the strip center on West Airport near McLain.
Two of the women left the scene, Houston police said. When they left, the women reportedly told a male suspect about the argument.
Police say the man then got into his truck, drove through the parking lot and shot the other two women.
One of the 18-year-olds was shot in the arm, and the other was shot in the leg. Police say they are both in stable condition.
The suspect drove away. Police had not released a suspect description.