Tuscon Massacar

so in  class today Mr.Palo was talking bout Tucson massacre, what i don't get is why/how would they let a guy in with a gun...dont they have like little mettal thing that gose in front of the room? how could the radio do such a thing ti make them convonce a guy to kill this women, dosent this world know bout 1st and 2nd amendment freedom of speech and all the other stuff. this world is going down hill from what everyone is doing.how can they just point fingers and have a day of respect of all they do is just go back and fourth.this world in messed up!