Question

skull (see x - ray scan on the left) and strands of his hair that were found.
ötzis belongings are also treated with the utmost care. these objects are just as valuable as ötzi himself for telling about his life and times. even microscopic grains of pollen and scraps of moss can be important clues. by analyzing the plant materials found on ötzi and his equipment, scientists were able to figure out that he lived in what is now northern italy.
how did ötzi die?
there have been many theories about how ötzi died. at first scientists thought he might have been lost or injured in a surprise snowstorm and died from the cold. then, in june 2001, doctors studying new x - rays discovered a shadowy image of something embedded deep within ötzis back. to learn more, they used ct scans. what they found shocked them.
the image was that of an arrowhead!

Explanation:

The text describes how scientists used CT scans to study Ötzi. The key detail about an arrow possibly killing Ötzi is supported by the discovery of an arrowhead via CT scans, which is a crucial piece of evidence.

Answer:

CT scans showed an arrowhead.