Reward: 25000 Exp
Don't let White escape the island
It is time for the last quest and a fight with the last boss. It is worth mentioning, that in the room behind you can find a workshop and medkits #1. There are also many gas tanks on the roof, as well as explosives planted on barrels #2 (you have to hold action key to activate a bomb, when it explodes it creates a wall of fire for few moments, which set fire on zombies crossing it).
There is also a lot of ammo there. It might be useful because you'll have to face several waves of soldiers first #1. Do not waste your ammo on White, because you're not able to kill him right now. Once you dealt with soldiers, White will order to execute Order 66 and you will be attacked by infected soldiers #2.
It is not worth fighting with them all the time. Try to move forwards #1, until you reach the stairs leading to the heliport. A cut-scene activates in that moment and you see White being bitten by his infected wife. He is taking an antidote however its effect is contrary to desired effects. Now you have to fight Infected White #2. This struggle is not easy. The monster charges at you all the time so you have to dodge and counterattack him immediately with your melee weapons.
You can try to lure him on the roof, where you can use gas tanks to burn him #1. Once he is dead, the last cut-scene activates ending the game #2.