Ran until his legs were screaming in pain as well . Ran until even that pain burnt away and he knew he should be on the ground asphyxiating , gasping and wheezing and choking for air - except he was n't . He could run for - god - damned - EVER now .

Question: What may be the reason for him running so furiously ?
Answer: Adrenaline is coursing through them .They need to make it back home .Someone is chasing them .They need to run in order to survive .