Stalker: Call of Pripyat → Quests → Hunt for the Chimera
Gonta, having learned of Danila and Glukhar's deaths, will ask us to help him hunt the chimera. If we decide to do this, we need to meet at 3 AM. Then head to the Emerald, catch the sleeping chimera off guard, and kill it. The chimera is somehow odd; it barely resists even at maximum fire, so a couple of bursts from an AK (if not less) will suffice.
Gonta will reward you with an SPSA-14 shotgun and direct you to Zveroboy for the reward money. Reporting the mission to him will net you 2,000 rubles.
Source: gamer.ru
See also:
Pirate Invasion. Terraria event