You must play the last mission of 'The Man who was there' to understand this one better. You can get that from my profile.

This mission may seem a bit too hard for some people who do not use good tactics while shooting and fighting in missions. It is very much possible that you get killed in he mission but if you use your brain to complete this mission then it is very easily possible to do that. I have completed the mission and therefore am I saying so. Now also to tell you that there are pickups which may help you in completing the mission (M4, Health, Hand Grenade, Bazoka).

*SPOILERS*

1. Just after the little timeout the police will start entering the place and your enemies will attack you..you have to hide instead of fight to avoid getting killed.
2.Then you may take the pickups which are very much hidden.
3. After that you have to fight them all by hiding and killing technique continuously until you kill them all!