Mark Ruffalo and Chris Evans were full of praise a young boy who stepped in to save his sister from a dog attack.The story of young Bridger was posted on Instagram by his aunt Nikki Walker, who started an account on the social media site just to share the incident.“My nephew is a hero who saved his little sister from an attacking dog. He, himself, took on the attack so that the dog wouldn’t get his sister,” she wrote, alongside a picture of Bridger displaying his extensive injuries.