Dog bites

It's a beautiful sunny day, so you decided to go running. Suddenly from the bushes next to the trail runs a snarling dog and bites into a forearm a young man who runs towards you. The man tries to fight off the dog, falls on the ground and hits his head. He stays laying on the ground and the dog runs away. What will you do?
I will try to run after the dog and catch him or at least make a picture of him.
I will check the health condition of the wounded man and call an ambulance.
I will check the health condition of the wounded man and give him first aid. I will also call an ambulance and the police and ask people who are around and saw the attack to stay there as witnesses for police.
I will place a tourniquet above the elbow to prevent blood loss. Then I will call an ambulance and the police.