One month after its Falcon 9 “anomaly,” Washington Post reports that a SpaceX employee paid a visit to United Launch Alliance’s headquarters. ULA is a SpaceX competitor, and its facilities overlook the launch pad, and that may have been enough to raise some questions. But there was more: SpaceX had seen something abnormal on the ULA roof right before the explosion.

After pulling in all available video footage and photographs of the explosion, SpaceX noticed an oddity, the Post reports: There was a dark spot on ULA’s roof, which then turned into a white spot. It could’ve been nothing; it could’ve been a laser; it could’ve been that guy from the grassy knoll. SpaceX didn’t know, so an employee wandered over to find out. ULA didn’t really take kindly to the employee’s request.

But first, some quick background. On September 1, SpaceX was set to test-fire its Falcon 9 rocket. The rocket would’ve eventually launched Mark Zuckerberg’s AMOS-6 satellite up into space, but instead — against all expectations and for no apparent reason — the whole thing blew up. It didn’t take long for people to start crying foul, and SpaceX CEO Elon Musk did nothing to quash these rumors. He actually fanned the flames: He went on Twitter and started tweeting cagey comments. One person asked him whether something could’ve hit the rocket. He responded: “We have not ruled that out.”

Meanwhile, YouTube videos surfaced claiming to prove that a UFO did it. Some thought it was an alien UFO — those darn aliens, rushing to stop humans from populating the universe — and others thought it could’ve been a drone, or some other literal unidentified flying object. Footage of the seconds leading up to the explosion showed birds and bugs flitting, but — right when the rocket blew up — one object flew by ridiculously fast and in a straight line.

The explosion in super slo-mo, with the unidentified object flying past.
The explosion in super slo-mo, with the unidentified object flying past.

SpaceX began a comprehensive investigation, and has since never stopped calling the explosion an “anomaly.” On September 23, SpaceX wrote:

At this stage of the investigation, preliminary review of the data and debris suggests that a large breach in the cryogenic helium system of the second stage liquid oxygen tank took place.

But the next day, after blogs around the world took that to mean it was case-closed, SpaceX added a comment: “[Updated 09/24: At this time, the cause of the potential breach remains unknown.]“

Since then, SpaceX has said that it’s just doing due diligence, crossing off possible causes one by one. And that’s what the employee said he or she was doing over at ULA. The ULA employee, however, didn’t let SpaceX enter. Instead, the employee called in the Air Force, which is helping SpaceX with the investigation. The Air Force investigators found nothing suspicious on the roof.

Musk, after announcing his Mars colonization plans, mentioned the investigation. “We’ve eliminated all of the obvious possibilities for what occurred there,” he said. “So what remains are the less probable answers.” Those less probable answers are likely not aliens, but another industry competitor knocking down the forerunner is not unfathomable.

Photos via YouTube / US Launch Report