Farmiliar Stranger

It was around 8:30pm on a Friday night, he was walking down a four wheel drive track when he hear a very light scream in the distance. He assumed it was just some kids playing so he kept walking, until he heard it again. At this point he knew someone was in trouble, He ran for his life hoping that he could help this person. He ran for about 100 meters when i came to the end of the track and looked around, one of the first thing i saw was a figure of what seemed to be a girl about 15 years old being held by a 40 year old looking man. When the man saw him, he dropped the girl and legged it around the corner, He sprinted over the woman who was busy crying obviously shaken up.
Being obviously more fit due to his youthful age, he came up behind the man and tackled him. With sweat pulling around his brow and dirt in his mouth, the man struggled to free himself from his grapple and he (seeing he was losing) hit the man in back just a bit above the spine causing the man to be visibly shaken and subdued him. After ensuring he had subdued him, he reached for his pocket to grab his phone and started calling 911. Almost immediately, he stopped, neck stiffened with his mouth agape as blood drew from it, he touched his chest and falls exposing a knife-wielding figure behind him. It was the 15 year old she looked at the man that had been tackled and he smiled at him.