In 1991 the perfectly preserved remains of a man were found in ice in the South Tyrol. He was found to date to around 3300BC and was given the name Ötzi. He has been the subject of research studies and TV programmes ever since, but only recently has his cause of death been confirmed by analysis of CT scans. This brief article on the EurekAlert website gives the bare facts:

Analysis of the CT images showed a lesion of the dorsal wall of the left subclavian artery, the artery underneath the clavicle, caused by an earlier, already-detected arrowhead that remains in the back. In addition, a large haematoma could be visualized in the surrounding tissue. By incorporating historic as well as modern data on the survivalship of such a severe lesion, the scientists concluded that the Iceman died within a short time due to this lesion.
“Such obvious proof of a vascular lesion in a body of this historic age is unique, and it helped to determine the cause of this extraordinary death without a destructive autopsy. We look forward to further investigating the circumstances surrounding the Iceman’s sudden death,” explains Dr. Dr. Rühli.

In other words, it has been determined that he died from a lesion to an artery near his neck, caused by an arrowhead that was still embedded in his body when he was found.

For a digestible overview of the discovery of Otzi and the subsequent research into his life and death, see the summary on the BBC website from 2002.