An apparent ritual mass sacrifice–including decapitations and a royal beer bash–is coming to light near a pre-Inca pyramid in northern Peru, archaeologists say.

Excavations next to the ancient Huaca Las Ventanas pyramid first uncovered bodies in August, and more have been emerging since then from a 50-by-50-foot (15-by-15-meter) pit.

The pyramid is part of the Sicán site, the capital of the Lambayeque people–also known as the Sicán–who ruled Peru’s northern coast from about A.D. 900 to 1100.