The victim called police to report the shooting around 10:40 a.m. He said he was in his car in the eastern part of the parking lot when a man approached his window, pulled out a gun and demanded his property, BART police Lt. Aaron Ledford said.
When the victim refused to comply, the suspect shot him in the arm, Ledford said.
The victim then drove away and called for help. He was taken to a hospital to be treated for wounds that are not believed to be life-threatening, he said.
No arrests have been made in connection with the shooting.
BART service was not affected.
Anyone with additional information about the shooting or the suspect's whereabouts is asked to call BART police detectives at (510) 464-7040.