After doing a couple of missions when you arrive into the town of Wellsprings you will be given a quest to stop the bandits from making RC car bombs. This quest will be issued by the sheriff; also he will provide you with the means of making your own car bomb
Proceed into the lair which is guided by your mini-map. When you take out the top portion of the bunker use the elevator to decend to the second floor. Silently dispose of the first guard with the crossbow/windsticks and use an RC car to kill the 3 unsuspecting enimies around the corner.
With in this mission it is possible to get :
The Silent But Deadly achievement in RAGE worth 29 pointsStealth kill 10 Enemies with the Striker Crossbow The Debunked achievement in RAGE worth 13 pointsComplete Shrouded Bunker in the Campaign
Silent but deadly achievement can be unlock if you have already been killing a couple mutants or unsuspecting pmcs' through-out the campain already
Debunked is unlocked after you have completed this mission for the sheriff.
*** If you have any question on how and when this quest pops up just shoot me an e-mail and I will contact you back. Also if I missed anything, please use the comment section to address it so I can change whatever it may be.***