NBC News correspondent Richard Engel revealed Thursday that his six-year-old son has died.
"Our beloved son Henry passed away. He had the softest blue eyes, an easy smile and a contagious giggle," Engel posted on Twitter. "We always surrounded him with love and he returned it, and so much more."
Engel documented his son's journey with Rett syndrome, a genetic neurological disorder that causes developmental delays. In March, he posted that his son had "taken a turn for the worse."
Months later, however, Engel posted a video of his son appearing to make progress.
"Henry was able to briefly support himself in a seated position during physio for the first time in a long time," Engel said. "Go Henry!"
Texas Children's Hospital, where Henry was being treated, posted a tribute to the six-year-old on Thursday.
"His loving and endearing smile, and the way he connected with his eyes, stole my heart from the time I met him," said Dr. Huda Zoghbi. "His quiet fight against this terrible disease was incredible."