This guide will explain the various steps needed to get this achievement, all the tools needed and where to get the “collectibles” to finally get your hands on the Boomstick from Hell. Let’s hop right into it!
You’ll need a bunch of items to progress through the level just as if you were playing it normally, But make sure you hold onto a set of keys. You’ll need them to open 2 doors that are needed for this achievement.
Other than that just play through the level following the tasks: you’ll need a red keycard, then a blue one, bolt cutters and finally a fire extinguisher.
Open it with your keys, but hold onto them, there’s another door you need the keys for. Once inside you’ll find the candle in the corner to your immediate left.
The candle will be sitting in its back. Hop onto the truck and grab it.
Make your way through the room, the candle is inside the foot locker on the far right.
This is where you’ll need the keys for the last time. Open the door after the guy closes it with the keys (it might take a bit for the prompt to pop up), kill the guy inside (which will give you the “It wasn’t an infection” achievement in case you didn’t have it already), and grab the diary from the couch.
Hold ‘E’ at the centre of the table and you’ll get a “summoning” propt, at the end of which you’ll spawn the Boomstick you were looking for.
Congratulations! You’ve got your well deserved achievement!