One person [person 1] says she is sickened and numbed by the number of killings in this country in which a gun was used. This was a reaction to one of the latest school killings. The other person [person 2] responds by saying people have been killing each other long before guns were invented. 'Don't blame the device.' Is this a straw man fallacy or what?

Person one makes an emotive statement - not a factual claim. Person 2's response could be considered a strawman since it addresses an argument person 1 never made—an argument that claims nobody was murdered before guns (of course people have been killing each other before guns). If an argument could be inferred from person 1's statement, then it might be that guns have led to more deaths than a time before guns—an argument which would require support and elucidation.

Personally, I would avoid calling either party out on fallacious reasoning. All too often the argument gets derailed by chasing claims of fallacies when the focus should be on the content of the original argument. If I were person 2, rather than assume an argument or claim was being made, I would ask what exactly she is claiming before creating an argument.

Focus on good communication, not on winning an imaginary argument.