To get the PK Crossbow in Dying Light 2, you need to assign at least four of the seven installations to Peacekeepers. When you assign a fourth install to the Peacekeepers, you will be rewarded with the Crossbow Pack, which means that the PK Crossbow, along with various blueprints for Elemental Bolts, will automatically be added to your inventory. If you have already assigned four or more Survivor Facilities, there is currently no way to get the Crossbow Pack without starting a new game from scratch. Sorry, but this is one of the downsides of Dying Light 2 Stay Human which doesn’t have a manual save system.
The different types of bolts are as follows (and this is how you switch between them):
Crossbow bolts: These just do regular damage, much like arrows.
Stun Bolts: These briefly immobilize enemies they hit.
Impact bolts: These knock enemies into the air. The funniest bolts, by far.
Slashing bolts: Make enemies bleed, so they lose health over time.
Freeze bolts: Like Stun Bolts, these immobilize and damage enemies, but they also deal bonus damage over time.
Toxic Bolts: Like slashing bolts, these deal damage over time, with the added bonus that they also cause enemies to vomit, making them slow and vulnerable. Toxic effect does not work on Infected.
Related: All Peacekeeper and Survivor upgrades in Dying Light 2 Stay Human
You can’t sell the PK Crossbow (although you can drop it), and we couldn’t find a vendor that sells bolts for it, so you have to craft them all yourself. You will need lots of scraps and feathers.