Right away, you'll have to protect Shane's truck from any attackers. Ride on top of the truck and quickly snipe the weak points of any enemies that show up, or rush ahead and melee them. They like to hide in alleys. Use your minimap and continuously ping to find them as soon as possible and take them out before they get close to the truck. When you find cars full of enemies, unload on the cars themselves to destroy them with the enemies inside. If you get seperated from the truck, it'll show up as an objective marker on your map, so get to it.
A few quick blasts should be enough to take out the cars that block your path. They get strangely light after they blow up. Enemy cars show up as yellow rectangles on your minimap, so take them all out as soon as you see them. This mission is pretty straightforward. Clearing this mission unlocks drive by shooting events in Seattle. Stop 10 of them to complete a challege and get 5 SP.
NEXT: Violence in Seattle