If by "credible news organization" you mean MSNBC, CNN, The Huffington Post or The Washington Times they are all liberal leaning news sources and often times choose not to report on incidents or news that is pro gun. Major news outlets are the most biased both left or right. The small Mom and Pop news outlets I find often report more facts without the slant.
I disagree, large media outlets need veiwership to sell product. Without viewship, they would cease to exist. If they lose credibilty then who would wish to tune into that. Small internet outlets have nothing to lose, they dont fact check nor do even wish to do so. Their intregity isnt on the line and so they can print whatever. This is a prime case. Dont get me wrong, the large media outlets do have a political agenda and Fox News and MSNBC are the worst.
You're right of course that most large media, print and broadcast, have a political bias but you're also correct that they understand their credibility is essential to their survival, particularly in the digital world we're in where any asshole can pretend to be a publisher or journalist and the more sensational their crap, the more page views they get and the more they make off advertising. The "credible" media will skew the news left or right depending on their bias, but at base, they don't usually fuck with the facts of a story, particularly one that's being well-covered.
BurnnBright makes a good point: who do you believe? A good approach is to believe no one - take nothing at face value. If you wish to be well informed, and get as close to the "truth" of something as you can, you need to read multiple sources covering the same story. But take those sources from the major news outlets: the big newspapers, and Fox, CBS, CNN, NBC, ABC, etc.. - the more credible news agencies. Also include in your diet the foreign press (try bbc.co.uk and afp.com) which offer insight you don't get in America.