Does violent video games really affect young children?

My husband let's my 8 yr old son play these violent games,Such as Scarface and GTA,(grand theft auto).I've told him that I don't feel comfortable him playing these types of games,cause of the swearing and shooting etc.He lets him play these games to get a break from him,but I feel that he can do something else,like read a book,do these games really affect the young mind of child,and my husbands excuse is that my son knows the difference between real life and game playing,so my son knows not to take any of this serious.But he shouldn't be knowing this kind of stuff at all.What should I do?Seriously