Gears of War: Act 1 Fish in the Barrel, Fork in...

After a while, you'll be attacked by Locusts. The problem is rather obvious - one of them is shooting at you using Troika Gun. You'll have to flank it on the right and annihilate him. You won't encounter any enemies under the bridge except for few Drones, who should be easy to kill. You just need to be close enough.

Get into the empty fountain and take a position. Tremors and all-around shaking means a hole is opening somewhere close. You'll have to fight some Locusts one after another, but leaving the fountain isn't the best idea. Annihilate your enemies patiently and holes will close by themselves. After the fight is over, stock up on ammo. Pick up 6.Tag.

Now you need to decide which way to choose. If you want to follow this guide, pick right. At the end of the corridor send some ammo towards Troika post. Now you can use the gun to finish off remaining enemies. Go through the door.

You'll find yourself in a big hall and under Troika fire. Quickly, get to that room on the right. Now, get to the other side of the room and hide behind the container. Turn right, wreck the door, kill one more enemy and from the window shoot at the crew manning the Troika gun. Go down, take control over the gun and destroy the rest of incoming enemy's reinforcements. After a bit of talking kill one more wandering sheep behind the door and get through.