Here are a few key points to consider regarding this hadith:
1. The Prophet's knowledge comes from Allah, so if he said someone is from the people of Hell, it indicates their final destiny based on Allah's pre-decree, not necessarily their current state or actions.
2. Other hadith indicate people can change their final destiny through sincere repentance and good deeds until the very end. So the brave man could have potentially reformed.
3. We don't know all the details of his heart, intentions, beliefs etc. Only Allah knows what is truly in the hearts of people.
4. This was a lesson for the companions not to lose hope in Allah's mercy but to