Keep your guard up, stay aware of your surroundings, and never let one of these thugs get close to you - period. I've have personal experience. They are explosive, fast, strong, will out number, and attack when you have your guard down or least expect it.
I disagree: The argument seems to have escalated verbally for a while. The Marines were obviously outnumbered and in danger. If they had been carrying, the man with the knife should never have been allowed to get anywhere close, and probably would not even have tried.