That's the story in this article by Patrizia Pernter and colleagues:
A possible cause of death of the Iceman -- a ca. 5,300 BP natural human glacier mummy from the Tyrolean Alps -- is an intrathoracic stone arrowhead. The aim of this study was to prove radiologically his enigmatic cause of death. In August 2005, the Iceman underwent his first multislice computed tomography examination. As the main pathologic finding, the left dorsal subclavian artery contures shows a 13 mm-long part where the vessel wall is damaged and a 3 mm-long irregular pseudo-aneurysm -- a typical complication of a laceration of the subclavian artery. In the surrounding soft tissue a large haematoma is visible. Historic records highlight the fatal destiny of subclavian artery injuries e.g. due to massive active bleeding and shock-related cardiac arrest. Therefore, the Iceman's cause of death by an arrowhead lacerating among others the left subclavian artery and leading to a deadly hemorrhagic shock can be now postulated with almost complete certainty, especially when taking the environmental (3,210 meters above sea level) and historic (5,300 BP) settings into account.
But did he have the lactase persistence allele?
Pernter P, Gostner P, Vigl EE, Rühli FJ. 2007. Radiologic proof for the Iceman's cause of death (ca 5,300 BP). J Archaeol Sci (in press) doi:10.1016/j.jas.2006.12.019