Currently only in spanish, but the basis is the following. You can craft a “Wanted Poster” from the crafting menu. Having just one on you when you kill another player gives you a bounty, displayed on the buffs area. Then, you can use the poster to craft your reward.
Having more than 1 poster on you or moving the poster when you have the bounty makes you lose the reward. The bounty scales up with the target level, starting from lvl 5. Also, killing players with the “nearDeathTrauma” on them wont yield any reward.
The forum topic of the mod is here.