The problem is that the image was heavily edited -- cropped and mirrored -- to multiply the size of the crowd and make it look perfectly symmetrical. It's also been mislabeled, as the original photo was taken a week earlier at another anti-extradition rally.
The image is the first result of a Twitter search for "Hong Kong protests," with more than 28,000 likes and 8,000 retweets. It's also been reposted on Instagram by people including Nathan Law, founding chair of the pro-democracy group, Demosisto.
Lui cropped the original picture, which he shared June 10 on Instagram, and reflected it using Photoshop, he confirmed to CNN. He took the original shot, which shows a sea of protesters on Hennessey Road, on June 9 from a building "opposite Hysan mall and beside Sogo," he said.
"I was just trying to share the beauty of Hong Kong to everyone," Lui said, noting that the post's caption clearly states it's doctored. "People should have acknowledged that as I stated."
Organizers of the second march said around 2 million people took part, while police said it was 338,000 people.