Who is Cetius from The Campaigns of Alexander and what is their importance?

Cetius grew up with Alexander and was a part of the Macedonian army. During a drinking binge with Alexander and others, Cetius began bragging about his mighty powers as a soldier, even going so far as to claim he saved Alexander's life. Angry and drunk, Alexander killed Cetius, though he immediately regretted it. Alexander mourned for days over losing his childhood friend by his own hand.