It's difficult to determine much based on very little information, however it's also difficult to imagine a reason why these two Red Line trains should ever be this close together during revenue service, outside of a "rescue train" scenario. I'll be looking into this, for sure. Stay tuned for further updates.
Big question: did a track circuit malfunction on the Red Line near Rhode Island Avenue result in a near-miss this morning? I have submitted these questions to Metro, and am awaiting a response.
UPDATE: I received the following information from Ron Holzer at Metro:
A switch was “red,” which means trains are not supposed to pass. The signal was stuck on red after a train was dispatched into the yard. Technicians were on scene to manually move the switch back to its proper position.
The photo shows a train stopped at the signal because it was red. (This is the train that the photographer was on when he/she took the photo.) This train was given permission by our Operations Control Center to pass through the red signal after our track technicians finished their manual work and were safely away from the train.
The second train had just left the platform and stopped automatically, which is what is supposed to happen when a train is ahead of it within that short distance. This second train was then given permission by the Operations Control Center to move forward after the first train left the area.
The trains were a safe distance from each other the entire time and in separate circuits as noted by the wee-zee bond viewable between them. Operations Control Center staff and the train operators were well aware of what was going on the entire time.
UPDATE x2: Looking at an aerial view of the location, this appears to be an example of extreme coincidences resulting in this photo. The back end of the train the photographer was on happened to be at the very end of one block. Had the rear car been about 10 feet further back, that last block would have been occupied, and the approaching train would have stopped farther back, likely on the elevated track right outside of New York Avenue. A frightening sight for riders of both trains, to be sure, but in this instance the track circuits appear to have worked correctly. It's a bit unnerving, but it was timing and 'luck' that allowed for this photo to be taken. It was in fact a track SWITCH malfunction, not a track CIRCUIT malfunction, as was originally reported by WMATA's twitter.