This short but informative video is well worth watching - as well as photographs of the site, it shows some of the archaeological work and looks at post-excavation analysis of the skull itself.
Since they began digging in 2004, the team has excavated about 500 skeletons dating back some 500 years to the Inca civilization. One skull stood out—marked with what appeared to be the entrance wound from a musket ball. Edges of the hole in the skull were found to be impregnated with fragments of iron, a metal sometimes used for Spanish musket balls. It appears that a musket ball less than an inch (2.5 centimeters) wide punched into the back of the skull and passed through the head, leaving pieces of iron deep inside the bone. The body is thought to be the first forensically proven casualty of the Spanish conquest.