Keenan Cahill, the beloved YouTube star known for his lip-synching videos, died on Thursday from surgery complications. He was 27. Cahill was just an infant when he was diagnosed with Maroteaux Lamy Syndrome, a progressive condition that causes tissues and organs to enlarge and deteriorate at an accelerated rate. Cahill, who had created videos with Jennifer Aniston, Katy Perry, 50 Cent and many other stars, announced earlier this month that he was scheduled to have open heart surgery on Dec. 15. On a GoFundMe that announced his death, Cahill's family said the online star was recovering from the surgery when he suddenly developed complications Thursday. He will go down as one of YouTube's original stars, first going viral in 2010 and amassing over 500 million views and 700,000 subscribers over the years. “Rip Keenan Thank You for always making the world smile,” Pauly D wrote in a tweet that included a photo of the two performing together.