What's not mentioned in the article from AFP but was mentioned in the Bangkok Post was that the boy had admitted to committing the crime because he wanted to know what it was like to do things from GTA in real life.
Violent games may not lead to criminal behavior in most children, no. Given the number of games sold (millions) and the number of "copy-cat" activities (few), that is a given without statistics or research to show it. If violent video games leads to violent behavior, there should be kids running around shooting people in the streets, running over people with cars, and blowing #### up.
It doesn't mean it doesn't happen though. Give an unstable mind the right trigger, and a person will do almost anything. Video games are no different than TV and movies, crime novels, or even comic books.
Guns, video games, movies, and comic books don't kill people. People kill people.