In the days following several theories were presented, both paranormal and natural. Some believe it to be witchcraft, and others believe it may be the result of spirit activity. Meanwhile some sources like the Huffingtom Post suggested it was insects, though they couldn't point to any specific insects that known to behave like that. Locust are known to block out the sky like a dark cloud, but lack any sort of organizational skills. On the 15th, a statement came from Warwick Castle that they were testing fireworks to compliment the firing of a trebuchet fireball, and the black ring was a result of their tests.
But, say, does this look familiar?
The authenticity of Heflin's photos has long been debated. Skeptics pointed to lines in the copies while the originals were confiscated, but after their return, no such lines are found on the originals. Skeptics also point out that the fourth picture appears to be of a cloudy sky, while the other three appear to have clear skies, though this has been suggested to also be a copy related anomaly. They also point out that objects thrown/suspended in the air are easily photographed for hoaxes, but believers claim there are smoke trails behind the UFOs that are not so easily faked.
Rings have also been sighted over Ft Belvoir and King's Dominion, in Virginia. The park claims the rings were caused by one of their rides, Volcano: The Blast Coaster. And the military base claims theirs was an nuclear blast simulation.
Fire and explosions creating black rings? That sounds familiar.
And here's a faint ring from Texas:
Which may have had something to do with a thunderstorm.
Of course there are still UFO explanations for these cases out there, like this article on how UFOs are hiding in clouds over Ft Belvior:
But the general consensus seems to be that where there is smoke, there is fire.
So what does this mean for Heflin's photos? Well, it leave me a more skeptical then before. If the UFO could easily be something like a hubcap, and the smoke ring the result of a fire or explosion (he was rather close to a military base, and had said himself the UFO might be an experimental craft, so witnessing an experimental explosion like those from Ft Belvior is not too far out of the question, and perhaps the fourth picture was actually the first picture taken), then it's easily a hoax.