B.W.
Children pick up lots of things in school. And the amazing thing is, they hear everything, even teachers talking, they are all listening. My child has come home telling me stories of what she heard the teachers talking about. Thank goodness its all about pets and what the teachers have planned for the weekend but it shows how much they listen to everything.
If he was just saying, he was going to throw his dad in the trash, okay, he might be upset over something, but to say im going to shoot you, that will only come from hearing from somebody else who have said those words angrily or hearing kids play violently like with these super hero stuff.
Thats why I prefer Dora no matter how annoying and loud she could get compared to all the super hero stuff kids watch these days. At least Dora is all about exploring, helping others and teaching spanish.
Like the advice of another person, talk with his teachers. Kids are very impressionable.