You begin the level under fire.

Immediately backflip twice to a safe position.

There are 2 snipers in the building to the left: one in the raised alcove just to the right of the facade with the fancy columns, the other up on the roof.

You can kill the one in the alcove fairly easily by firing from the cover of the archway near the gate. Sidestep to the right just far enough that Lara can see the alcove, but not far enough for either sniper to target her.

Combine the crossbow with the laser sight and hold Look to use the sight. Then zoom in on the sniper's leg, which should be sticking out beyond the edge of the column. (Use the same controls as Duck/Crouch and Dash/Sprint to zoom in and out.) Fire two explosive arrows, or use pistol ammo with the laser sight bug to kneecap him. Normal arrows don't seem to work. If you see blood, you'll know your shots are connecting. Keep firing and after about 40 shots, he'll fall.

NOTE: If you missed the LASER SIGHT back in Alexandria, don't worry. You'll get it soon.

Step out a little farther to target the second sniper on the roof. He'll start firing grenades down at you, but in the PC version, at least, these don't do any damage. Use the crossbow + laser sight + pistol ammo as described above.

Or just kill him quickly with Uzis.

- OR -

Alternatively, take out the lower sniper by running across the street and positioning Lara very close to the ledge where he's standing.

Draw weapons (the shotgun works nicely) and jump in place...

...shooting at the peak of the jump.

When he's dead, climb up and take the REVOLVER he drops. Finally!

Then run back to the safe spot near the gate and use your new toy to kill the sniper on the roof.

Combine the REVOLVER and LASER SIGHT. (You may need to first separate the sight from the crossbow.) Draw the revolver and sidestep out until you can get a clear shot.

Use the laser sight to target the sniper's head or chest. You'll need to be quick, since he can shoot back, but one or two well-aimed shots should bring him down. If the grenades aren't hurting Lara, you can take your time and shoot pistol ammo with the revolver using the laser sight bug.

[City of the Dead Walkthrough]