explain the incident of mistaken identity

In Chapter Three, Pip sneaks out of the house and back to the marshes. He finds a man, wet and cold and dressed like a convict, but he turns out to be a different convict from the man who had threatened him the night before. This man has a badly bruised face and wears a broad-brimmed hat. He runs away from Pip without speaking to him. Pip finally finds his man and gives him the food. The man reacts with anger when Pip tells him about the other convict. Pip leaves him filing at his shackle and returns home.