It happened in the Auburn sand pit on Gracelawn Road around 2:20 p.m. Monday.
Investigators say 42-year-old Ryan Kane of Oxford was loading a logging truck when a log fell out of the cherrypicker and hit Thomas Staples, 57, also of Oxford.
Staples was taken to the hospital, where he later died from his injuries.
The victim was not an employee of the company. He was Kane's cousin and was there to observe Kane working.
Auburn police say this is not believed to be a workplace fatality.