Many of us have watched Richard Engel, NBC News’ chief foreign correspondent, for years. In Afghanistan, Russia, Ukraine, etc. Sadly, Richard Engel shared some other, very personal news with us all this week:  His six year old son Henry has passed away from Rett Syndrome.

Richard Engel shared on social media: “Our beloved son Henry passed away. He had the softest blue eyes, an easy smile and a contagious giggle. We always surrounded him with love and he returned it, and so much more. Mary and Richard.”

Henry suffered from a genetic disorder known as Rett syndrome, which is usually present in girls and occurs when genes on the x-chromosome mutate. The six-year-old was diagnosed was still an infant in 2017. The disorder affects cognitive and motor skills and prevents the brain from making connections after learning new abilities such as speech. Due to the rarity of the mutation in boys, Henry’s condition provided new insights for researchers that could help others affected by Rett syndrome in the future.

On May 31, Engel tweeted that Henry had “taken a turn for the worse. His condition progressed and he’s developed dystonia: uncontrolled shaking/stiffness. He was in the hospital for 6 weeks, but is now and getting love from brother Theo.”

In 2018, Engel told The Today Show that he and his wife began to notice early on that Henry wasn’t developing at a normal rate. He struggled to talk, walk and even sit up straight even before his second birthday.

In an essay Engle wrote earlier this year, he wrote about how valuable school in the pre-pandemic era was for Henry.” The kids would come up and kiss him, tussle his hair and bring him toys,” Richard explained in part. “He didn’t always respond as they expected, but the excitement in his eyes told them he enjoyed and appreciated it. Special needs kids have the most expressive eyes.”

Researches hope to use Henry’s case to better treat others affected by Rett syndrome moving forward. Engel wrote in a follow-up Tweet on Thursday that “researchers are making amazing progress using Henry’s cells to help cure RETT Syndrome so others don’t have to endure this terrible disease.” Engel also encouraged his followers to support the research that is being done at the Texas Children’s Hospital.