When you get past the first part of the chapter with the men shooting the transit cop, go down the steps to the left. Kill the man with the shotgun, then go down the steps to the left and kill all those men. When you are done there, look under the benches with the lockers on them. You will see some gas tanks. Shoot the top off them. They will explode and reveal a secret room down the hallway.
While at the inspection car, there is a door near it. Go inside the door and you will find cupboards. Inside the cupboards are shotgun and Beretta ammunition.
When you go downstairs, there will be three men waiting; one with a shotgun and two with pistols. In order to kill them, you must kill the main with the shotgun first. He will take your health down quickly. Jump and dive down the stairs then kill him.
Go to the area where the inspection car is found, where three men (one with a shotgun and two with Berretas) appear. There are two gas tankers below the lockers. If you shoot them, all the tankers in that area will explode.