the boy probably had intermittent explosive disorder, not really an example of "a stupid person influenced by videogames." i can see where the confusion might have happened in shooting, but the kid almost raped his mom, and that's something videogames don't really teach you. those who kill and don't regret doing so are most likely sociopaths and that's something you don't really acquire from killing in games either. The most games can do to a person is lower their reaction to more violent stimulus but people who end up doing dumb shit like this have a mental issue not related at all to games.
on a side note buying your kid a gun at 11 years old is a fucking stupid idea when 11 year olds have only begun the child development stage (the formal operational stage) where they learn how to logically break down the implications of their actions and how to solve their own problems.