Leonel Arias, 47, said he was playing a practical joke by wearing the Laden mask and jumping out with his airgun to scare several drivers on a narrow street in Carrizal de Alajuela, about 32 km north of San Jose.
But whenhe jumped out in front of taxi driver Juan Pablo Sandoval, the driver pulled out a gun and shot him twice in the stomach.
"For me and I think for anybody else at a time like that one thinks the worst and so I fired my gun," Sandoval said later.
Arias was hospitalized and was said to be in stable condition Wednesday.
Police declined to detain Sandoval, saying he believed he was acting in self-defense