Use the cardboard cut-outs as cover, then when you get close, kill the RED HWG.

From Create Your Own Story

The next cardboard cut out of a BLU medic pops up from its lowered position and you use it as cover. The HWG sees the cardboard cut out and unleashes a hail of bullets, leveling it. You jump from the shadows and slit your would-be killer's throat. The Scout, done jumping through the air, issues a challenge to you with some very obscene gestures and words. You respond by showing off your knife skills. He charges at you iwht a bat but you counter with a blow to his exposed armpit. You home in and the blade pierces the armpit and cuts the heart. The Scout goes down with a thud and you take his figure as a disguise.

You exit the red-stained room and look for your next objective.

You can:

Find the RED Sniper

Find and Disable the sentries