My 3yr old son has recently developed this liking to guns and shooting games. We don't have toy guns at home but he will pretend with his hand and pretend to shoot people. Is it okay?

Soon or later he will be exposed to more new things, either from TV or classmates. We can't always be there to shield our kids from negative influences. What we can do as a parent is to proper educate kids what gun is used for and why gun is dangerous.