Archaeologists at Cancuen found bones in a pool adjacent to the royal palace. As they continued to dig deeper, they continued to find more bones, so many that Dr. Demarest called in the Forensic Anthropological Foundation of Guatemala (FAFG) that specializes in researching modern massacres. They discovered that the bones were probably Mayan nobles, stabbed with spears, ritualistically dismembered and tossed in the pool.
NPR did an interview with Arthur Demarest about the massacre and how they were discovering what really happened. You can hear the interview and read more here:
National Geographic covered it here:
To find out more about the work of FAFG, see this Ted Talk by Fredy Peccarelli.