Also. As to why you don't hear stories about people "doing good" with firearms, but only the murders, sprees, etc., keep in mind that there's only so much available news space--only so many spots on the 11 o'clock news; only so much room on the front page of a paper or site. Somebody has to make choices about what to report/what to cover. And what to leave out.
While I don't want to get all conspiracy theory about "media bias" or whatever, I *have* heard that journalists describe themselves as liberal (as opposed to conservative) by a fairly large margin. If the people making these sorts of decisions believe, at their core, that guns do more harm than good... doesn't it make sense that such a preconception would affect their choices?
Maybe you're only hearing one kind of story because that's all they're choosing to tell you.