When you arrive at the scene of a knife injury, make sure that you are not in any danger at all. This may mean that you have to run away and then come back, but what you do not want, is more victims. Shout for help and keep constant vigilance. Get as much attention as possible, as not only will this scare away the possible attacker, but it will also hopefully attract more help. Obviously, call the emergency services as soon as possible, and since it is a knife crime injury, not just the ambulance will show up – expect the police to come as well.