Occasionally we use Photoblog to provide transparency to you about how we face difficult picture editing situations. This is one of those posts.

This picture was posted to yfrog today by Twitter user @jdivenere with this tweet: "Here's a pic of the gunman that my colleage [sic] at #discovery sent me."

These are some of the steps we have taken to verify that the picture was taken today at Discovery headquarters and is of the gunman.

• Using our @msnbc_pictures Twitter account, we "at-replied" to jdivenere: "can we use your friends photo, or have his contact"
• A few minutes later, jdivenere posted "I can no longer comment about this situation." We have no direct communication with either jdivenere, or with his friend who sent him the picture, and that last post sure doesn't encourage more messages/phone calls/etc (not that we are giving up).
• We do still know that jdivenere's Twitter profile lists the author as "Jason Divenere," and the bio says "I work for Discovery." An Internet search reveals a LinkedIn profile that fits that description and a cached High School alumni update page that also fits the bill, giving us a lot more circumstantial evidence that a guy named Jason Divenere works for Discovery in Chicago. Of course, we're still not any closer to being in touch with his friend...
• But we do know that a zoom-in on the Bing Maps aerial view of Discovery Communications Headquarters, at 1 Discovery Place in Silver Spring, MD, sure has similar looking semi-circular sidewalks to the one in the picture (zoom in below to see what I mean):

  View Larger MapDriving DirectionsView Bird's Eye

• So I'm starting to feel more comfortable that the picture was taken at Discovery HQ at least.
• But. . . Twitter user @kibrly is now claiming, in response to the picture, that "This is not the gunman. I work at Discovery, he is a police officer"-- so now we have more verification to do.

Given all that, the only place we are publishing this picture, at least for the moment, is right here in this post, to provide context to how we deal with breaking news photo research in social media. This is by no means the only photograph, video or Web page being actively investigated and researched by NBC News. We're dealing with this on a number of fronts today.

While we've had loose guidelines around this procedure for years, we're going to need to formalize them, and then continue to evolve them. We'll share what we come up with in updates to this post, and welcome your thoughts and suggestions in the comments below.

One question to get the discussion going: How much do you trust pictures you see in social media, or derived from there on Web sites? Are you cautious about believing captions? And does your level of trust vary between established news sites like msnbc.com and other places where you come across cell phone pictures purporting to show breaking news events?

One more question: Do you have any pictures from Silver Spring today? If so, please go to our First Person page to send them to us, and make sure you include contact information, so we can take steps to verify the images.

Update at 4:53 p.m. ET: We've posted our phone number to the yfrog post, hoping for more info. And Kurt Schlosser on our entertainment desk notes via email: "I just saw 3 cops on MSNBC TV and they were all wearing khaki shorts like the subject in the photoblog pic. for what that's worth."

Update at 5:17 p.m. ET:Click here to see a frame grab from MSNBC TV, showing law enforcement personnel in khaki shorts.