Disembark from the car and head to the marker. Press B to hack the wire and open the gates. Continue to the parking lot and take out all enemies there. Continue downstairs, and fight your way to parking lot B. Continue following your comrades until you need to breach the door.
Equip your gas mask when prompted, then continue upstairs. Fight your way through an office area. There's an ammo crate in the middle of the room before the large hall so make sure to use it to your advantage.
After clearing the area, continue upstairs and fight your way to the main trading room. You'll spot the nuke carrier there you don't chase him yet. Just kill everybody in sight then proceed in your pursuit. As soon as you reach outside the building, you'll have another achievement to unlock. If you're doing the campaign in Easy Mode, then good for you. Otherwise, you may want to retry it later in Easy difficulty since it is very hard to attempt this in Normal or Hard mode.
Dodging bullets is my specialty
To unlock "The Professional" achievement, you need to complete the street chase in less than 2 minutes, 30 seconds without dying. Stay on the left side of the street! Continue running and shoot only the enemies directly in front of you. Take note that the timer starts as soon as your character removes his gas mask.
After the sequence, continue pursuing the carrier until you finally catch up to him on the train platform. Kill the bastard in hand-to-hand combat and watch the following scenes.
This is the end