Then come to the other side of the building

and switch out the sniper rifle to cover the friendly troops on the street
Crouch behind cover, don't play for thrills, the enemy is no slouch. In addition to the street there will be enemies on the upper floors on the left side of the building, after the friendlies are safely through a large number of enemies will come from the street, it's time to run for your life. Follow your teammates to another block and go through a very country building with some enemies inside, but not much of a threat. After exiting the building you can see the marines that need rescuing, but a bomb was found under a nearby car. Follow the red wire that connects the bomb to the source, unplug the wire from the switch and get attacked by the enemy, follow the prompts to take out the enemy, unplug the second wire and return to the street you were on.