'Ax Men' Pilot William Bart Colantuono Killed in Freak 'Copter Crash

The badass log-slinging helicopter pilot from Season 3 of History Channel's "Ax Men" has been killed in a bizarre chopper accident ... and authorities are still not sure exactly what went wrong.

54-year-old William Bart Colantuono -- who flew a logging helicopter for a company called R&R Logging -- died while piloting his 'copter in an Oregon forest Tuesday. As usual, he had been using the helicopter to haul logs out of the forest.

Witnesses told police they saw William release his logs shortly before impact, indicating he knew there was a problem.

Witnesses said they also saw the rotor separate from the helicopter before the aircraft flipped and crashed upside down. The accident is still under investigation.