It started with the Twitter account @Murdered tweeting the message "What is ..." followed by a link to the above picture, which appeared to be a section of a photograph of a tree with something carved into its bark. Attempting to navigate to one of the picture's "files" parent folder results in being automatically redirected to an eidosinteractive.com subdomain. Ah ha!
Minutes later, we received an email from a Square Enix e-mail address (masquerading as an "@murdered.com" address) with the subject header "What is the hardest case to solve?" Contained inside was a second image, which combined perfectly with the image that had been tweeted earlier.
Naturally we decided to check out murdered.com, and were met by an image of the symbol scrawled on asphalt in chalk, accompanied by a link to the official twitter account and icons revealing the project's related platforms. A whois search revealed that the domain is registered to Naoto Sugiyama, a senior manager at Square Enix., and a glance at the site's source code revealed certain assets as being hosted on Eidos webspace.
Furthermore, Square Enix registered a Japanese trademark for "Murdered: Soul Suspect" back in December of last year, Siliconera reports. We've contacted both Square Enix and the murdered.com address and will update with any new discoveries we're able to make.
Update: Well, that was fun while it lasted. Square Enix has confirmed to us that Murdered: Soul Suspect is "an exciting new game from Square Enix which challenges players to solve possibly the hardest case of all," which obviously wasn't this case, since all we had to do was send an email and ask. Eidos' potential involvement, however, does remain a mystery.