document: The film director had originally meant to shoot the sunset, but pointed the drone downwards to return home when the battery ran low.
  It wasn't until he was going through his footage later that he saw the shot.
  Mr Li says he posted it online in a bid to find out who the pair are, but the photo is not entirely what it seems.
  "I was with a friend trying to get a good shot of the sunset but the drone battery was running low so we just pointed it down as it returned home, and I thought we'd just keep the camera rolling," Mr Li told the BBC.
  "I didn't notice anything interesting until I went through the footage later and saw this grassy rooftop."
  Mr Li, who was raised in the US but has family in Hong Kong, then posted the picture on Facebook hoping one of his friends would know the couple.
  From then, it "kinda just took off", he says.
  The shot, which he believes shows the roof of the J residence apartments in Hong Kong, was definitely not staged, says Mr Li.
  "So many people think that I staged the photo," he says. "I'm a filmmaker not a wedding photographer so I don't really have an incentive. It's really just a lucky catch."
  But he did make some adjustments to the original photo, which was taken on 28 September.
  The photo he captured shows two people standing near the couple's feet, presumably photographers, who Mr Li airbrushed out to make the couple stand out more.
  A person sprawled out on some seating in the corner, however, was spared the cut.
  Mr Li says he applied some colour correction to the image as well.
  For now, the identity of the couple - who might in real life not actually be a couple - remains a mystery, though Mr Li has made enquiries with the building's management who have yet to respond.
  But even if the photo fails to make it into the wedding books, he thinks it's a great metaphor for life in Hong Kong.
  "You usually see these really cold pictures of Hong Kong looking really crowded and grey, and here's this moment where two people are doing something very good and joyous.
  "It's like making your own oasis of joy in the city."
summary: A "lucky catch" is how Brandon Li describes the accidental drone shot he captured of "newlyweds" on a rooftop in Hong Kong.