Bridger Walker of Wyoming was bitten in the face and head several times by the German Shepherd mix after loading the siblings while playing in a garden on July 9.
His family said that when asked why he saved his sister, they said, “If someone were to die, I thought it should be me. “
The young boy – who is a huge Marvel fan – has been praised by celebrities such as Chris Evans, Mark Ruffalo, Tom Holland and Anne Hathaway.
Evans, who plays Captain America in the Marvel film franchise, told him, “Pal, you’re a hero. ”
The siblings were at a friend’s house at the time of the attack, said their aunt Nicole Walker in an Instagram post.
Bridger later told his family that the child with them had pointed to two dogs while they were in the garden, describing one as the “nice dog” and the other as the “bad guy”.
The “bad guy” loaded them on it, so Bridger stood between the dog and his sister to keep him from reaching him.
Instead of running away, the dog jumped up and grabbed Bridger’s cheek.
The six-year-old told his sister to run before he managed to free himself and lead her to another part of the garden where he hoped they would be safe.
The owners of the dog secured the dog and made Bridger run inside the house before calling the emergency services.
Bridger’s family said there was “a lot of blood,” and the firefighters who arrived at the scene asked to cut his shirt.
But Bridger refused, saying, “My mom loves me in this shirt.”
He was taken to hospital by ambulance, where he received 90 stitches in the face during an operation lasting almost two hours.
Bridger – who trains in jiu-jitsu – was told by a doctor that he was the “bravest patient” they had ever had, his family said in an Instagram post.
“The only time he cried was when he got the drip,” said the family.
Bridger has been described by his family as “absolute joy” and “full of love”.
They added that when the attack took place “it is not surprising that it intervened in a major way”.
The heroic actions of the six-year-old caught the attention of many movie stars, and he even received a video message from Evans.
In the comforting video shared by Bridger’s family, Evans said to the young boy, “Hey Bridger, Captain America here. How’s it going buddy?
“So I read your story, I saw what you did. Now, I’m sure you’ve heard a lot about it in the past two days, but let me be the next to tell you – buddy, you’re a hero.
“Your sister is so lucky to have you as an older brother.” Your parents must be so proud of you. “