Back in April, just as the Celtics were gearing up to try and make a deep run in the NBA Playoffs, Isaiah Thomas’ sister Chyna died in a car accident in Washington. She was 22.

Thomas was obviously heartbroken over it and briefly considered sitting out the remainder of the postseason. He eventually decided to play, but in a statement he released a few days after Chyna’s death, he said, "The pain I am feeling right now is impossible to put into words."

Thomas and his family continue to mourn the loss of Chyna, and it looks like Thomas did something pretty special for his dad James to honor his sister. On Tuesday, Thomas, in collaboration with The Players’ Tribune, released a short documentary called Book of Isaiah II that chronicles some of the things he’s been dealing with in recent months, both on and off the court. It features Thomas talking about everything from the hip injury that has sidelined him so far this season to fatherhood.

But the best moment comes when Thomas surprises his dad by handing him a box that has a chain with a photo of Chyna on it inside. His dad gets very emotional upon seeing the chain and tells Thomas he plans on taking his other chains off and wearing it right away.

"I wanted to give something to my dad for the passing of my little sister," Thomas says in the doc, "so my little sister could always be with him. I got one of the best pictures of my little sister and thought of the idea of a chain."

You can check out the moment in the clip above. You can also watch the entire documentary in the video at the top.